TUI windows do not need to store their type

TUI windows do not need to store their type

TUI windows no longer need to store their type -- there's only a
single spot that uses this information, and it can be changed to use
dynamic_cast.  (It could be cleaned up even more, by using a virtual
method, but I haven't done so.)  This patch removes the "type" field
from tui_gen_win_info, and this in turn allows removing a couple of
enumerator constants.

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

	* tui/tui.h (enum tui_win_type) <LOCATOR_WIN, DATA_ITEM_WIN>:
	Remove constants.
	* tui/tui-winsource.h (struct tui_source_window_base)
	<tui_source_window_base>: Remove parameter.
	* tui/tui-winsource.c
	(tui_source_window_base::tui_source_window_base): Remove
	parameter.
	(tui_source_window_base::refill): Update.
	* tui/tui-stack.h (struct tui_locator_window)
	<tui_locator_window>: Update.
	* tui/tui-source.h (struct tui_source_window) <tui_source_window>:
	Default the constructor.
	* tui/tui-regs.h (struct tui_data_item_window)
	<tui_data_item_window>: Default the constructor.
	(struct tui_data_window) <tui_data_window>: Likewise.
	* tui/tui-disasm.h (struct tui_disasm_window) <tui_disasm_window>:
	Default the constructor.
	* tui/tui-data.h (struct tui_gen_win_info) <tui_gen_win_info>:
	Default the constructor.
	<type>: Remove.
	(struct tui_win_info) <tui_win_info>: Default the constructor.
	* tui/tui-data.c (tui_win_info::tui_win_info): Remove.
	* tui/tui-command.h (struct tui_cmd_window) <tui_cmd_window>:
	Default the constructor.

Change-Id: I594cd07d2e0bba71ad594a6fb263904ce2febcd6