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.