Better support for Fortran 9x.
* automake.in: Add "fc" and "ppfc" languages for Fortran 9x.
* doc/automake.texi (Fortran 9x Support): New section.
* lib/Automake/Variable.pm (%_ac_macro_for_var): Add AC_PROG_FC.
* tests/compile_f90_c_cxx.test: New file.
* tests/ext.test: Add AC_PROG_FC.
* tests/f90only.test: New file.
* tests/link_f90_only.test: New file.
* tests/Makefile.am (TESTS): Add new tests.