Revert these two patches:

Revert these two patches:

2006-04-06  Eric Blake  <ebb9@byu.net>
* lib/autoconf/lang.m4 (_AC_COMPILER_EXEEXT_O): Inside cache
check, s/ac_exeext/ac_cv_exeext/.  Fixes regression introduced
2006-04-01.

2006-04-01  Stepan Kasal  <kasal@ucw.cz>
Clean up _AC_COMPILER_EXEEXT* macros.
* lib/autoconf/lang.m4 (_AC_COMPILER_EXEEXT_DEFAULT): Don't try to
  detect exeext, it will be done by _AC_COMPILER_EXEEXT_O; just set
  ac_file to the name of the default output file and call
  _AC_COMPILER_EXEEXT_WORKS.  Move the definition of ac_files and the
  initial `rm' of the candidate files...
(_AC_COMPILER_EXEEXT): ... here and simplify them.  Moreover, use
  the same list in subsequent `rm' calls, and for the temporary
  redefinition of ac_clean_files; call _AC_COMPILER_OBJEXT at the end,
  and don't call the other _AC_COMPILER_EXEEXT_* macros directly, use...
(_AC_COMPILER_EXEEXT_TESTS): ... this new macro.
(_AC_COMPILER_EXEEXT_O): Don't export ac_cv_exeext, it's not needed (or
  no longer needed) by libtool.  Make it a cache check.
(_AC_COMPILER_EXEEXT_CROSS): Remove the comment, it was obviously
  copied here by mistake.
(AC_NO_EXECUTABLES): Redefine _AC_COMPILER_EXEEXT_TESTS, not
  _AC_COMPILER_EXEEXT.
* lib/autoconf/c.m4 (AC_PROG_CC, AC_PROG_CXX, AC_PROG_OBJC): Do not call
  _AC_COMPILER_OBJEXT directly.
* lib/autoconf/fortran.m4 (_AC_PROG_FC): Likewise.