Bug 327916 - DW_TAG_typedef may have no name

We already accepted DW_TAG_typedef without a name for Ada. But g++ for
OpenMP can also emit such nameless DW_TAG_typedefs. Just accept them.
Also fix up anonymous enum and typedef printing in tytypes.c.

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13718 a5019735-40e9-0310-863c-91ae7b9d1cf9