x86, signal: Cleanup ifdefs and is_ia32, is_x32

Use config_enabled() to cleanup the definitions of is_ia32/is_x32. Move
the function prototypes to the header file to cleanup ifdefs,
and move the x32_setup_rt_frame() code around.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1343171129-2747-2-git-send-email-suresh.b.siddha@intel.com
Merged in compilation fix from,
Link: http://lkml.kernel.org/r/1344544736.8326.17.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/signal.h

@@ -31,6 +31,10 @@ typedef struct {
 	unsigned long sig[_NSIG_WORDS];
 } sigset_t;
 
+#ifndef CONFIG_COMPAT
+typedef sigset_t compat_sigset_t;
+#endif
+
 #else
 /* Here we must cater to libcs that poke about in kernel headers.  */