This change prompted by a problem report by Andrey Simonenko in
<http://lists.gnu.org/archive/html/bug-autoconf/2006-12/msg00026.html>.
* doc/autoconf.texi (Defining Symbols): AC_DEFINE works for
object-like macros only, in the traditional portable character
set.
* lib/autoconf/general.m4 (AC_DEFINE_TRACE_LITERAL):
Warn about attempts to define things that are not identifiers.
* lib/autoconf/fortran.m4 (_AC_FC_WRAPPERS): Rewrite to avoid
awful hack that AC_DEFINEd macro names containing parentheses.