c++: rtti cleanups

c++: rtti cleanups

Here are a few cleanups from the modules branch.  Generally some RAII,
and a bit of lazy namespace pushing.

	gcc/cp/
	* rtti.c (init_rtti_processing): Move var decl to its init.
	(get_tinfo_decl): Likewise.  Break out creation to called helper
	...
	(get_tinfo_decl_direct): ... here.
	(build_dynamic_cast_1): Move var decls to their initializers.
	(tinfo_base_init): Set decl's location to BUILTINS_LOCATION.
	(get_tinfo_desc): Only push ABI namespace when needed.  Set type's
	context.