[PR86379] do not use TREE_TYPE for USING_DECL_SCOPE

[PR86379] do not use TREE_TYPE for USING_DECL_SCOPE

It's too risky to reuse the type field for USING_DECL_SCOPE.
Language-independent parts of the compiler, such as location and
non-lvalue wrappers, happily take the TREE_TYPE of a USING_DECL as if
it was a type rather than an unrelated scope.

For better or worse, USING_DECLs use the non-common struct so we can
use the otherwise unused result field.  Adjust fallout, from uses of
TREE_TYPE that were supposed to be USING_DECL_SCOPE, to other
accidental uses of TREE_TYPE of a USING_DECL.

for  gcc/cp/ChangeLog

	PR c++/86379
	* cp-tree.h (USING_DECL_SCOPE): Use result rather than type.
	* name-lookup.c (strip_using_decl): Use USING_DECL_SCOPE.
	* search.c (protected_accessible_p): Follow USING_DECL_DECLS.
	(shared_member_p): Likewise.
	(lookup_member): Likewise.
	* decl.c (grok_special_member_properties): Skip USING_DECLs.
	* semantics.c (finish_omp_declare_simd_methods): Likewise.
	(finish_qualified_id_expr): Do not call shared_member_p with
	a dependent expr.

for  gcc/testsuite/ChangeLog

	PR c++/86379
	* g++.dg/cpp0x/pr86379.C: New.

From-SVN: r268851