* lib/autoconf/general.m4: Revert AC_TRY_EVAL and AC_TRY_COMMAND,
since evidently some packages rely on the old, broken behavior.
Problem reported by Ralf Wildenhues in
<http://lists.gnu.org/archive/html/autoconf-patches/2006-05/msg00160.html>.
(AC_TRY_EVAL, AC_TRY_COMMAND, _AC_EVAL): Go back to the
pre-2006-05-26 definitions, but leave in the comments that
these macros are dangerous and should not be used.
(_AC_DO_ECHO): Renamed from _AC_EVAL_ECHO. All callers changed.
(_AC_DO): Renamed from _AC_EVAL. All callers changed.
(_AC_DO_STDERR): Renamed from _AC_EVAL_STDERR. All callers changed.
(_AC_DO_VAR): Renamed from AC_TRY_EVAL.
(_AC_DO_TOKENS): Renamed from AC_TRY_COMMAND.