move the demangled_names_hash into the per-BFD

move the demangled_names_hash into the per-BFD

This moves the demangled_names_hash from the objfile into the per-BFD
object.  This is part of the objfile splitting project.

The demangled names hash is independent of the program space.  And, it
is needed by the symbol tables.  Both of these things indicate that it
must be pushed into the per-BFD object, which this patch does.

Built and regtested on x86-64 Fedora 18.

	* objfiles.c (free_objfile_per_bfd_storage): Delete the
	demangled_names_hash.
	(free_objfile): Don't delete the demangled_names_hash.
	* objfiles.h (struct objfile_per_bfd_storage)
	<demangled_names_hash>: New field.
	(struct objfile) <demangled_names_hash>: Move to
	objfile_per_bfd_storage.
	* symfile.c (reread_symbols): Don't delete the
	demangled_names_hash.
	* symtab.c (create_demangled_names_hash): Update.
	(symbol_set_names): Update.