Factor configure-time gcc version checks (patch 1/4 for PR 7305)

[DJ Delorie]

> OK to install?

Sorry for missing this.  This is OK with me.  Please make sure both
src and gcc are updated, for those files that are common (TL and
config).

At some future time, it might be useful to handle the case where an
in-tree gcc is not available, and it may use $(CC) somehow.  But
that's just food for thought.

> Richard
> 
> 	* configure.in: Include config/gcc-version.m4.  Use TL_AC_GCC_VERSION
> 	to set gcc_version_trigger.  Remove some now-redundant AC_SUBSTs.
> 	* configure: Regenerate.
> 
> config/
> 	* config/gcc-version.m4: New file.
> 
> fastjar/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.
> 	* configure, aclocal.m4, Makefile.in: Regenerate.
> 
> fixincludes/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.
> 	* aclocal.m4: Include ../config/gcc-version.m4.
> 	* configure: Regenerate.
> 
> gcc/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.  Remove
> 	now-redundant AC_SUBSTs.
> 	* aclocal.m4: Include ../config/gcc-version.m4.
> 	* configure: Regenerate.
> 
> libffi/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.
> 	* configure, aclocal.m4, Makefile.in: Regenerate.
> 	* include/Makefile.in, testsuite/Makefile.in: Regenerate.
> 
> libgfortran/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.
> 	* configure, aclocal.m4, Makefile.in: Regenerate.
> 
> libjava/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.
> 	* configure, aclocal.m4, Makefile.in, gcj/Makefile.in: Regenerate.
> 	* include/Makefile.in, testsuite/Makefile.in: Regenerate.
> 
> libmudflap/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.
> 	* configure, aclocal.m4, Makefile.in: Regenerate.
> 	* testsuite/Makefile.in: Regenerate.
> 
> libobjc/
> 	* configure.ac: Use TL_AC_GCC_VERSION to set gcc_version.
> 	* configure, aclocal.m4: Regenerate.