Introduce two TUI source window methods

Introduce two TUI source window methods

This adds two methods to the TUI source window.  These are just
renamings of existing functions.  It also changes the source window
list to have a more precise type, letting the code be more type-safe.
This will be useful again later.

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

	* tui/tui-winsource.h (tui_refill_source_window)
	(tui_set_is_exec_point_at): Don't declare.
	* tui/tui-winsource.c (tui_update_source_windows_with_addr)
	(tui_source_window_base::refill): Rename from
	tui_refill_source_window.
	(tui_source_window_base::do_scroll_horizontal): Update.
	(tui_source_window_base::set_is_exec_point_at): Rename from
	tui_set_is_exec_point_at.
	(tui_update_all_breakpoint_info): Update.
	* tui/tui-stack.c (tui_show_frame_info): Update.
	* tui/tui-layout.c (show_data): Add cast.
	* tui/tui-hooks.c (tui_redisplay_source): Call refill method.
	* tui/tui-data.h (struct tui_source_window_base) <refill,
	set_is_exec_point_at>: New methods.
	(tui_source_windows, tui_add_to_source_windows): Update types.
	(tui_add_to_source_windows): Remove redundant declaration.
	* tui/tui-data.c (source_windows): Store tui_source_window_base.
	(tui_source_windows): Change return type.
	(tui_clear_source_windows_detail): Update.
	(tui_add_to_source_windows): Change type of parameter.
	(tui_free_all_source_wins_content): Update.