Add "usage" text to all TUI command help

This adds "usage" text to the help for all all the TUI commands.  In
some cases the usage is borderline, but I tend to think being complete
is preferable.

2020-02-22  Tom Tromey  <tom@tromey.com>

	* tui/tui-win.c (_initialize_tui_win): Add usage text.
	* tui/tui-stack.c (_initialize_tui_stack): Add usage text.
	* tui/tui-regs.c (_initialize_tui_regs): Add usage text.
	* tui/tui.c (_initialize_tui): Add usage text.

Change-Id: I727f7a7cfc03efa248ef98f30a18be393819e30b


5 files changed