gcc-2.7.2.3 fails on __extension__

[Marek Michalkiewicz]

Trying to build CVS gcc using the good old stable gcc-2.7.2.3
(as shipped with Debian 2.1) fails in cppinit.c and cpplex.c -
this version knows about designated initializers, but not about
the __extension__ keyword added there yesterday.

I suggest to test GCC_VERSION in ansidecl.h and #define __extension__
empty if the compiler used is too old, but I'm not sure exactly in
which version __extension__ appeared.  Someone here will know :-).

Thanks,
Marek