Change "winheight" resizing to use new layout code

Change "winheight" resizing to use new layout code

The "winheight" command resizes a specified window, resizing the other
windows in the layout to adapt.  In the current code, this is done by
examining each possible layout separately.  The new layout code has a
more general approach to handling this, and this patch simply removes
the old code in favor of a call into the new layout engine.

gdb/ChangeLog
2019-12-11  Tom Tromey  <tom@tromey.com>

	* tui/tui-win.c (tui_set_win_height_command): Call
	tui_adjust_window_height.
	(tui_adjust_win_heights, new_height_ok): Remove.
	* tui/tui-layout.h (tui_adjust_window_height): Declare.
	* tui/tui-layout.c (tui_adjust_window_height): New function.

Change-Id: I6bb681375a46adc8d29fd06f581deed4e078e78a