[tree-ssa] Enable warnings for libbanshee

[Daniel Berlin]

>
> I'm much more inclined to just require turning off libbanshee if the 
> host compiler doesn't support these things (There has been 1 person 
> who has tried to compile libbanshee with a compiler that isn't gcc, 
> AFAIK)
> --Dan
>

Screw it, i'll fix them all.

Of course, some of them are just completely worthless.
Like the variadic macros warning, which occurs on this code:


#ifdef HAVE_VARIADIC_MACROS
#define fail(args...) __fail(__FILE__, __LINE__, __FUNCTION__, args)
#else
void fail(const char *fmt, ...);
#endif

(HAVE_VARIADIC_MACROS is only defined if it's GNU C or a C99 compiler)