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

	* top.c (gdb_secondary_prompt_depth): Delete.
	(gdb_in_secondary_prompt_p): Add ui parameter.  Use it.
	(gdb_readline_wrapper_cleanup, gdb_readline_wrapper): Adjust to
	per-UI gdb_secondary_prompt_depth.
	* top.h (struct ui) <secondary_prompt_depth>: New field.