Change tui_update_source_window for better type safety

Change tui_update_source_window for better type safety

tui_update_source_window can only be called for source and disassembly
windows, so change the argument type to enforce this at compile time.

gdb/ChangeLog
2019-06-25  Tom Tromey  <tom@tromey.com>

	* tui/tui-winsource.h (tui_update_source_window)
	(tui_update_source_window_as_is): Change parameter type.
	* tui/tui-winsource.c (tui_update_source_window): Change win_info
	to be a tui_source_window_base.
	(tui_update_source_window_as_is): Likewise.
	* tui/tui-win.c (make_visible_with_new_height): Update.