respect iso c namespace in stdio.h and wchar.h regarding va_list

despite declaring functions that take arguments of type va_list, these
headers are not permitted by the c standard to expose the definition
of va_list, so an alias for the type must be used. the name
__isoc_va_list was chosen to convey that the purpose of this alternate
name is for iso c conformance, and to avoid the multitude of names
which gcc mangles with its hideous "fixincludes" monstrosity, leading
to serious header breakage if these "fixes" are run.

arch/powerpc/bits/alltypes.h.sh

@@ -21,6 +21,7 @@ TYPEDEF int ssize_t;
 TYPEDEF int ptrdiff_t;
 
 TYPEDEF __builtin_va_list va_list;
+TYPEDEF __builtin_va_list __isoc_va_list;
 
 #ifndef __cplusplus
 TYPEDEF long wchar_t;