Remove tui_clear_source_windows_detail

Remove tui_clear_source_windows_detail

The calls to tui_clear_source_windows_detail in tui_add_win_to_layout
aren't needed, because (after the resize unification) resizing will
update the window contents.  Removing these calls lets us remove
several other things as well.

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

	* tui/tui-data.h (tui_clear_source_windows_detail): Don't
	declare.
	* tui/tui-layout.c (tui_add_win_to_layout): Don't call
	tui_clear_source_windows_detail.
	* tui/tui-winsource.h (struct tui_source_window_base)
	<clear_detail>: Don't declare.
	* tui/tui-winsource.c (tui_source_window_base::clear_detail):
	Remove.
	* tui/tui-data.c (tui_clear_source_windows_detail): Remove.