Remove TUI data window special case

Remove TUI data window special case

The TUI has a couple of special cases for updating the data window:
one in tui_rl_other_windowand one in tui_set_focus_command.  As part
of the project to remove references to globals, I wanted to remove
these calls; but when I did, some simple operations (like "C-x o")
would cause the register window to blank.

This fixes the underlying problem by arranging for the data window's
refresh_window method to call the superclass method first, and then to
refresh the child windows.  Then the special cases can be removed.

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

	* tui/tui.c (tui_rl_other_window): Update.
	* tui/tui-wingeneral.c (tui_data_window::refresh_window): Call
	superclass method first.  Always iterate over regs_content.
	(tui_unhighlight_win, tui_highlight_win): Use refresh_window
	method.
	* tui/tui-win.c (tui_set_focus_command): Update.