use __extension__ for long long on gcc >= 2.8 and egcs, and provide a

use __extension__ for long long on gcc >= 2.8 and egcs, and provide a

* configure.in: use __extension__ for long long on gcc >= 2.8 and
egcs, and provide a G_GINT64_CONSTANT wrapper so -ansi -pedantic
compiles clean.

* glib.h: make the endian x86 asm __const__ so the compiler can do
better optimizations. Also remove the cc clobber, these shouldn't
be changing condition codes. Ditch some redundant casts. Add an
optimization for 64-bit endian conversions in x86. Use constant
wrapper for the generic method.

* testglib.c: use constant wrappers for 64-bit constants

-Yosh