Throw a "quit" on a KeyboardException in py-framefilter.c

Throw a "quit" on a KeyboardException in py-framefilter.c

If a C-c comes while the Python code for a frame filter is running, it
will be turned into a Python KeyboardException.  It seems good for
this to be treated like a GDB quit, so this patch changes
py-framefilter.c to notice this situation and call throw_quit in this
case.

gdb/ChangeLog
2018-03-26  Tom Tromey  <tom@tromey.com>

	* python/py-framefilter.c (throw_quit_or_print_exception): New
	function.
	(gdbpy_apply_frame_filter): Use it.

gdb/testsuite/ChangeLog
2018-03-26  Tom Tromey  <tom@tromey.com>

	* gdb.python/py-framefilter.exp: Add test for KeyboardInterrupt.
	* gdb.python/py-framefilter.py (name_error): New global.
	(ErrorInName.function): Use name_error.