Use std::move in a few places

Use std::move in a few places

This patch adds std::move to few spots where it seems to be missing.

Regression tested by the buildbot.

ChangeLog
2017-08-14  Tom Tromey  <tom@tromey.com>

	* break-catch-throw.c (handle_gnu_v3_exceptions): Use std::move.
	* break-catch-syscall.c (create_syscall_event_catchpoint): Use
	std::move.
	* break-catch-sig.c (create_signal_catchpoint): Use std::move.