[binutils-gdb] Always process target events in the main UI

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT c61db772bf5dc21bf8e0db9acfa8796804f945ab ***

Author: Pedro Alves <palves@redhat.com>
Branch: master
Commit: c61db772bf5dc21bf8e0db9acfa8796804f945ab

Always process target events in the main UI

This makes target events always be always processed with the main UI
as current UI.  This way, warnings, debug output, etc. are always
consistently sent to the main console.

gdb/ChangeLog:
2016-06-21  Pedro Alves  <palves@redhat.com>

	* event-top.c (restore_ui_cleanup): Make extern.
	* infrun.c (fetch_inferior_event): Always switch to the main UI.
	* top.h (restore_ui_cleanup): Declare.