- Macro: AC_DECL_YYTEXT
     Define `YYTEXT_POINTER' if `yytext' is a `char *' instead of a
     `char []'.  Also set output variable `LEX_OUTPUT_ROOT' to the base
     of the file name that the lexer generates; usually `lex.yy', but
     sometimes something else.  These results vary according to whether
     `lex' or `flex' is being used.

 - Macro: AC_PROG_AWK
     Check for `mawk', `gawk', `nawk', and `awk', in that order, and
     set output variable `AWK' to the first one that it finds.  It
     tries `mawk' first because that is reported to be the fastest
     implementation.

 - Macro: AC_PROG_CC
     Determine a C compiler to use.  If `CC' is not already set in the
     environment, check for `gcc', and use `cc' if that's not found.
     Set output variable `CC' to the name of the compiler found.

     If using the GNU C compiler, set shell variable `GCC' to `yes',
     empty otherwise.  If output variable `CFLAGS' was not already set,
     set it to `-g -O2' for the GNU C compiler (`-O2' on systems where
     GCC does not accept `-g'), or `-g' for other compilers.

     If the C compiler being used does not produce executables that can
     run on the system where `configure' is being run, set the shell
     variable `cross_compiling' to `yes', otherwise `no'.  In other
     words, this tests whether the build system type is different from
     the host system type (the target system type is irrelevant to this
     test).  *Note Manual Configuration::, for more on support for
     cross compiling.

 - Macro: AC_PROG_CC_C_O
     If the C compiler does not accept the `-c' and `-o' options
     simultaneously, define `NO_MINUS_C_MINUS_O'.

 - Macro: AC_PROG_CPP
     Set output variable `CPP' to a command that runs the C
     preprocessor.  If `$CC -E' doesn't work, it uses `/lib/cpp'.  It
     is only portable to run `CPP' on files with a `.c' extension.

     If the current language is C (*note Language Choice::.), many of
     the specific test macros use the value of `CPP' indirectly by
     calling `AC_TRY_CPP', `AC_CHECK_HEADER', `AC_EGREP_HEADER', or
     `AC_EGREP_CPP'.

 - Macro: AC_PROG_CXX
     Determine a C++ compiler to use.  Check if the environment variable
     `CXX' or `CCC' (in that order) is set; if so, set output variable
     `CXX' to its value.  Otherwise search for a C++ compiler under
     likely names (`c++', `g++', `gcc', `CC', `cxx', and `cc++').  If
     none of those checks succeed, as a last resort set `CXX' to `gcc'.

     If using the GNU C++ compiler, set shell variable `GXX' to `yes',
     empty otherwise.  If output variable `CXXFLAGS' was not already
     set, set it to `-g -O2' for the GNU C++ compiler (`-O2' on systems
     where G++ does not accept `-g'), or `-g' for other compilers.

     If the C++ compiler being used does not produce executables that
     can run on the system where `configure' is being run, set the shell
     variable `cross_compiling' to `yes', otherwise `no'.  In other
     words, this tests whether the build system type is different from
     the host system type (the target system type is irrelevant to this
     test).  *Note Manual Configuration::, for more on support for
     cross compiling.

 - Macro: AC_PROG_CXXCPP
     Set output variable `CXXCPP' to a command that runs the C++
     preprocessor.  If `$CXX -E' doesn't work, it uses `/lib/cpp'.  It
     is only portable to run `CXXCPP' on files with a `.c', `.C', or
     `.cc' extension.

     If the current language is C++ (*note Language Choice::.), many of
     the specific test macros use the value of `CXXCPP' indirectly by
     calling `AC_TRY_CPP', `AC_CHECK_HEADER', `AC_EGREP_HEADER', or
     `AC_EGREP_CPP'.

 - Macro: AC_PROG_GCC_TRADITIONAL
     Add `-traditional' to output variable `CC' if using the GNU C
     compiler and `ioctl' does not work properly without
     `-traditional'.  That usually happens when the fixed header files
     have not been installed on an old system.  Since recent versions
     of the GNU C compiler fix the header files automatically when
     installed, this is becoming a less prevalent problem.

 - Macro: AC_PROG_INSTALL
     Set output variable `INSTALL' to the path of a BSD compatible
     `install' program, if one is found in the current `PATH'.
     Otherwise, set `INSTALL' to `DIR/install-sh -c', checking the
     directories specified to `AC_CONFIG_AUX_DIR' (or its default
     directories) to determine DIR (*note Output::.).  Also set the
     variable `INSTALL_PROGRAM' to `${INSTALL}' and `INSTALL_DATA' to
     `${INSTALL} -m 644'.

     This macro screens out various instances of `install' known to not
     work.  It prefers to find a C program rather than a shell script,
     for speed.  Instead of `install-sh', it can also use `install.sh',
     but that name is obsolete because some `make' programs have a rule
     that creates `install' from it if there is no `Makefile'.

     A copy of `install-sh' which you may use comes with Autoconf.  If
     you use `AC_PROG_INSTALL', you must include either `install-sh' or
     `install.sh' in your distribution, or `configure' will produce an
     error message saying it can't find them--even if the system you're
     on has a good `install' program.  This check is a safety measure
     to prevent you from accidentally leaving that file out, which
     would prevent your package from installing on systems that don't
     have a BSD-compatible `install' program.

     If you need to use your own installation program because it has
     features not found in standard `install' programs, there is no
     reason to use `AC_PROG_INSTALL'; just put the pathname of your
     program into your `Makefile.in' files.

 - Macro: AC_PROG_LEX
     If `flex' is found, set output variable `LEX' to `flex' and
     `LEXLIB' to `-lfl', if that library is in a standard place.
     Otherwise set `LEX' to `lex' and `LEXLIB' to `-ll'.

 - Macro: AC_PROG_LN_S
     If `ln -s' works on the current filesystem (the operating system
     and filesystem support symbolic links), set output variable `LN_S'
     to `ln -s', otherwise set it to `ln'.

     If the link is put in a directory other than the current
     directory, its meaning depends on whether `ln' or `ln -s' is used.
     To safely create links using `$(LN_S)', either find out which
     form is used and adjust the arguments, or always invoke `ln' in
     the directory where the link is to be created.

     In other words, it does not work to do
          $(LN_S) foo /x/bar

     Instead, do

          (cd /x && $(LN_S) foo bar)

 - Macro: AC_PROG_RANLIB
     Set output variable `RANLIB' to `ranlib' if `ranlib' is found,
     otherwise to `:' (do nothing).

 - Macro: AC_PROG_YACC
     If `bison' is found, set output variable `YACC' to `bison -y'.
     Otherwise, if `byacc' is found, set `YACC' to `byacc'.  Otherwise
     set `YACC' to `yacc'.