* cppinit.c (builtin_array): Update.
        (init_builtins): Flag builtins to warn if redefined or
        undefined.  Define __GXX_WEAK as a normal macro.
        * cpplib.c (do_undef): Warn if flagged NODE_WARN.
        * cpplib.h (NODE_WARN): New flag.
        * cppmacro.c (builtin_macro): Remove handling of __GXX_WEAK__.
        Handle __STDC__ as a builtin only on Solaris.
        (warn_of_redefinition): Renamed from check_macro_definition.
        Reverse sense of test.  Always warn if NODE_WARN.
        (_cpp_create_definition): Use warn_of_redefinition.  Flag
        any macro beginning with "__STDC_" to require a mandatory
        warning if redefined or undefined.

From-SVN: r40053