gdb: remove breakpoint_pointer_iterator

Remove the breakpoint_pointer_iterator layer.  Adjust all users of
all_breakpoints and all_tracepoints to use references instead of
pointers.

Change-Id: I376826f812117cee1e6b199c384a10376973af5d
Reviewed-By: Andrew Burgess <aburgess@redhat.com>
11 files changed