Globs that are in symbol table can be un-globbed

Globs that are in symbol table can be un-globbed

If a symbol table entry is undefined when a glob is assigned into it, it
gets a FAKE flag which makes it possible to be downgraded when non-glob
is subsequently assigned into it. It doesn't really matter, until we
decide to localize it -- it wouldn't be possible to restore its GP upon
context return if it changed type, therefore we must not do that.

This patch turns off FAKE flag when localizing a GV and restores it when
the context is left. A test case is included.