GDB was not restoring the signal handler before returning when a notification
was received.  This patch fixes it.

2013-06-04  Sergio Durigan Junior  <sergiodj@redhat.com>
	    Pedro Alves  <palves@redhat.com>

	* remote.c (remote_wait_as): Restore signal handler before returning
	when GDB gets a notification.
Fixing ChangeLog entry of the last commit.