configure.ac-early:
dnl Some compilers (e.g., AIX 5.3 cc) need to be in c99 mode
dnl for the builtin va_copy to work. With Autoconf 2.60 or later,
-dnl AC_PROG_CC_STDC arranges for this. With older Autoconf AC_PROG_CC_STDC
+dnl gl_PROG_CC_C99 arranges for this. With older Autoconf gl_PROG_CC_C99
dnl shouldn't hurt, though installers are on their own to set c99 mode.
-AC_REQUIRE([AC_PROG_CC_STDC])
+gl_PROG_CC_C99
configure.ac:
gl_STDARG_H