Change tui_update_exec_info to be a method

Change tui_update_exec_info to be a method

This changes tui_update_exec_info to be a method on
tui_source_window_base.

gdb/ChangeLog
2019-08-13  Tom Tromey  <tom@tromey.com>

	* tui/tui-winsource.h (struct tui_source_window_base)
	<update_exec_info>: Declare.
	(tui_update_exec_info): Don't declare.
	* tui/tui-winsource.c (tui_update_source_window_as_is)
	(tui_source_window_base::refresh_all)
	(tui_update_all_breakpoint_info): Update.
	(tui_source_window_base::update_exec_info): Rename from
	tui_update_exec_info.
	* tui/tui-stack.c (tui_show_frame_info): Update.