[PATCH] variable.c (rb_global_tbl): convert to id_table
variable.c (rb_global_tbl): convert to id_table
Mainly this is to reduce casting a tiny amount; and
probably nothing depends on the order of globals.
Likely no measurable memory usage improvement as globals
are not common, but maybe some weird code out there benefits.
I'm also working on patches to convert ivar-related tables
to id_table; but figured I'd get this out of the way, first.
There's also: https://bugs.ruby-lang.org/issues/11614
("[RFC] use id_table for constant tables") but that is
actually most likely to cause breakage in class name resolution.