Simplify use of map_matching_symbols in ada-lang.c
I noticed that ada-lang.c creates a lambda to call
aux_add_nonlocal_symbols. However, this code can be simplified a bit
by changing match_data to implement operator(), and then simply
passing the object as the callback. That is what this patch
implements.
gdb/ChangeLog
2021-03-26 Tom Tromey <tom@tromey.com>