* cppspec.c: Insert -no-gcc into command line unless -gcc was
        given by user.
        * gcc.c (default_compilers): Define __GNUC__ and
        __GNUC_MINOR__ only if -no-gcc was not given.
        * objc/lang-specs.h: Likewise.
        * cpp.texi: Document -x and -std options; explain that -lang
        is no longer supported.  Minor related corrections.

From-SVN: r26990