Revert this (for now):

Revert this (for now):
| * lib/autoconf/c.m4 (AC_PROG_CC, AC_PROG_CXX, AC_PROG_OBJC): Call
|   _AC_COMPILER_EXEEXT instead of m4_expand_once([_AC_COMPILER_EXEEXT])
| * lib/autoconf/fortran.m4 (_AC_PROG_FC): Likewise.
| * lib/autoconf/lang.m4 (_AC_COMPILER_EXEEXT_TESTS): On subsequent
|   calls, for a new language, only check that the compiler works.
| (AC_NO_EXECUTABLES): Change the redefinition of
|   _AC_COMPILER_EXEEXT_TESTS so that on subsequent calls, it checks
|   that the new language's compiler works if ac_no_link=no, and
|   does nothing otherwise.