c++: local function versioning [PR104669]

c++: local function versioning [PR104669]

There were two problems with this testcase: we weren't copying the target
attribute from the second declaration to the global alias for the first
one (duplicate_decls hunk), and then we were treating the third one as
matching the earlier one even though both are versioned (decls_match hunk).
The latter change required a fix to find_last_decl (used for attribute
mismatch warnings) to give up if we see a versioned function, as in that
case we can't determine whether the decls match, because we are still in the
process of setting the attributes on the new decl.

	PR c++/104669

gcc/cp/ChangeLog:

	* decl.cc (decls_match): Compare versions even if not recording.
	(duplicate_decls): Propagate attributes to alias.
	* decl2.cc (find_last_decl): Give up if versioned.

gcc/testsuite/ChangeLog:

	* g++.target/i386/mv31.C: New test.