Remove some TUI static allocations

Remove some TUI static allocations

The TUI statically allocates the "execution_info" for the source and
disassembly windows.  However, there's no deep reason to do this, and
this approach makes it harder to allow multiple such windows.

This patch removes the static data and changes the code to simply
allocate these windows as needed.  This required pushing some code
into the tui_gen_win_info destructor, but that seems like a good idea
anyhow.

gdb/ChangeLog
2019-06-25  Tom Tromey  <tom@tromey.com>

	* tui/tui-layout.c (make_source_or_disasm_window): Always use
	init_and_make_win for EXEC_INFO_WIN.
	* tui/tui-data.h (struct tui_gen_win_info) <~tui_gen_win_info>: No
	longer inline.
	(struct tui_win_info) <~tui_win_info>: Inline.
	(tui_source_exec_info_win_ptr, tui_disassem_exec_info_win_ptr):
	Don't declare.
	* tui/tui-data.c (source_win, disasm_win): Remove globals.
	(tui_source_exec_info_win_ptr, tui_disassem_exec_info_win_ptr):
	Remove.
	(tui_initialize_static_data): Update.
	(~tui_gen_win_info): Handle more cleanup here.
	(~tui_source_window_base): Delete "execution_info".
	(~tui_win_info): Move code to ~tui_gen_win_info; remove.