Remove some cleanups from search_minsyms_for_name

Remove some cleanups from search_minsyms_for_name

This changes struct collect_minsyms to use a std::vector, which
enables the removal of a cleanup from search_minsyms_for_name.  This
also changes iterate_over_minimal_symbols to take a
gdb::function_view, which makes a function in linespec.c more
type-safe.

ChangeLog
2018-04-05  Tom Tromey  <tom@tromey.com>

	* minsyms.h (iterate_over_minimal_symbols): Update.
	* minsyms.c (iterate_over_minimal_symbols): Take a
	gdb::function_view.
	* linespec.c (struct collect_minsyms): Remove.
	(compare_msyms): Now a std::sort comparator.
	(add_minsym): Add parameters.
	(search_minsyms_for_name): Update.  Use std::vector.