Use a std::vector for ada_exceptions_list

Use a std::vector for ada_exceptions_list

Change ada_exceptions_list to return a std::vector and fix up the
users.  This allows removing a cleanup in MI.

gdb/ChangeLog
2017-09-29  Tom Tromey  <tom@tromey.com>

	* mi/mi-cmd-info.c (mi_cmd_info_ada_exceptions): Update.
	* ada-lang.h (struct ada_exc_info): Remove typedef.  Declare
	operator< and operator==.
	(ada_exceptions_list): Return a std::vector.
	* ada-lang.c (ada_exc_info::operator<): Rename from
	compare_ada_exception_info.
	(ada_exc_info::operator==): New.
	(sort_remove_dups_ada_exceptions_list): Change type of
	"exceptions".
	(ada_add_standard_exceptions, ada_add_exceptions_from_frame)
	(ada_add_global_exceptions): Likewise.
	(ada_exceptions_list_1): Return a std::vector.
	(ada_exceptions_list): Likewise.