restore_selected_frame: tweak warning.

restore_selected_frame: tweak warning.

I noticed SRC_LINE has special handling within print_stack_frame (mid
statement handling), so I audited all uses, and noticed the one in
restore_selected_frame.  I actually added this warning myself back in
2008, but reading back, I think we can do better.  "reparsed frame" is
probably confusing to users.

Old:

 warning: Couldn't restore frame #2 in current thread, at reparsed frame #0

 45         w = 0;
 (gdb)

New:

 warning: Couldn't restore frame #2 in current thread.  Bottom (innermost) frame selected:
 #0  foo () at foo.c:45
 45         w = 0;
 (gdb)

Tested on x86_64 Fedora 17.

gdb/
2013-08-30  Pedro Alves  <palves@redhat.com>

	* thread.c (restore_selected_frame): Use SRC_AND_LOC, and change
	warning text.