Set TUI locator height to 1

Set TUI locator height to 1

The TUI has long had code to resize the locator, using 2 as the
height.  However the code has "1" in a comment, like:

    locator->resize (2 /* 1 */ ,

This patch fixes the resizing code to set the height to 1.  Doing this
revealed what was probably the reason for setting the height to 2 in
the first place: this caused the locator window to scroll.  However,
this is easily handled by calling scrollok on the locator window.

gdb/ChangeLog
2019-09-20  Tom Tromey  <tom@tromey.com>

	* tui/tui-win.c (tui_resize_all, tui_adjust_win_heights): Use 1 as
	height for locator.
	* tui/tui-stack.c (tui_locator_window::rerender): Call scrollok.
	* tui/tui-layout.c (show_source_disasm_command, show_data)
	(show_source_or_disasm_and_command): Use 1 as height for locator.