Merge refresh and refresh_window methods

Merge refresh and refresh_window methods

Earlier refactorings introduced the refresh and refresh_window
methods, following the previous TUI code.  However, these methods are
essentially the same, so this patch merges them.  It also removes some
redundant refresh_window calls, because the execution window is
updated automatically by the corresponding source (or disassembly)
window.

gdb/ChangeLog
2019-07-17  Tom Tromey  <tom@tromey.com>

	* tui/tui-winsource.c (tui_show_exec_info_content): Don't call
	refresh_window.
	* tui/tui-wingeneral.c (tui_gen_win_info::refresh_window): Call
	touchwin.
	(tui_data_window::refresh_window): Call refresh_window on data
	items.  Always call superclass refresh_window.
	(tui_win_info::refresh): Remove.
	(tui_source_window_base::refresh_window): Update.
	(tui_refresh_all): Update.
	* tui/tui-layout.c (show_source_disasm_command): Remove call to
	refresh_window.
	(show_source_or_disasm_and_command): Likewise.
	* tui/tui-data.h (struct tui_win_info) <refresh>: Remove.
	(struct tui_source_window_base) <refresh>: Likewise.