gdb/python: convert gdb.Symtab to use gdbpy_registry

This commit converts gdb.Symtab to use gdbpy_registry for lifecycle
management. Since gdb.Symtab only holds on the struct symtab * (and
prev/next links) the default invalidator can be used.

Approved-By: Tom Tromey <tom@tromey.com>
1 file changed