c++: Relax attribute on friend declaration checking [PR100596]

c++: Relax attribute on friend declaration checking [PR100596]

It turned out that there are codebases that profusely use GNU attributes
on friend declarations, so we have to dial back our checking and allow
them.  And for C++11 attributes let's just warn instead of giving
errors.

	PR c++/100596

gcc/cp/ChangeLog:

	* cp-tree.h (any_non_type_attribute_p): Remove.
	* decl.c (grokdeclarator): Turn an error into a warning and only
	warn for standard attributes.
	* decl2.c (any_non_type_attribute_p): Remove.
	* parser.c (cp_parser_elaborated_type_specifier): Turn an error
	into a warning and only warn for standard attributes.
	(cp_parser_member_declaration): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/friend7.C: Turn a few dg-warnings into dg-errors.
	Remove dg-errors for GNU attributes.
	* g++.dg/ext/attrib63.C: Remove dg-error.
	* g++.dg/cpp0x/friend8.C: New test.