Introduce gdb_breakpoint_up

Introduce gdb_breakpoint_up

This introduces gdb_breakpoint_up, a unique_ptr typedef that owns a
breakpoint.  It then changes set_momentary_breakpoint to return a
gdb_breakpoint_up and fixes up the fallout.  This then allows the
removal of make_cleanup_delete_breakpoint.

Once breakpoints are fully C++-ified, this typedef can be removed in
favor of a plain std::unique_ptr.

gdb/ChangeLog
2017-11-04  Tom Tromey  <tom@tromey.com>

	* breakpoint.c (set_momentary_breakpoint): Return
	breakpoint_up.
	(until_break_command): Update.
	(new_until_break_fsm): Change argument types to
	breakpoint_up.
	(set_momentary_breakpoint_at_pc): Return breakpoint_up.
	(do_delete_breakpoint_cleanup, make_cleanup_delete_breakpoint):
	Remove.
	* infcmd.c (finish_forward): Update.
	* breakpoint.h (set_momentary_breakpoint)
	(set_momentary_breakpoint_at_pc): Return breakpoint_up.
	(make_cleanup_delete_breakpoint): Remove.
	(struct breakpoint_deleter): New.
	(breakpoint_up): New typedef.
	* infrun.c (insert_step_resume_breakpoint_at_sal_1): Update.
	(insert_exception_resume_breakpoint): Update.
	(insert_exception_resume_from_probe): Update.
	(insert_longjmp_resume_breakpoint): Update.
	* arm-linux-tdep.c (arm_linux_copy_svc): Update.
	* elfread.c (elf_gnu_ifunc_resolver_stop): Update.
	* infcall.c (call_function_by_hand_dummy): Update