Per https://sourceware.org/bugzilla/show_bug.cgi?id=24480 toplevel
types were broken by
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=93b8bea4143cafae79076076c64aaa4c46a9b73c
because it only set list_in_scope in start_sym_tab. With type-units,
It also needs to be set when re-opening a symtab.

Mark