PR10573: Squash duplicate inline instances

PR10573: Squash duplicate inline instances

In C++, identical functions included in multiple CUs will get merged at
link time into a single instance.  We need to make sure that inlines
within those merged functions are not probed multiple times.

* tapsets.cxx (inline_instance_info::operator<): Used for set support.
  (dwarf_query::handle_query_module): Clear inline_dupes on each module.
  (query_dwarf_inline_instance): Squash this inline instance if it's
  already in the inline_dupes set.