Use new and delete for tui_gen_win_info

Use new and delete for tui_gen_win_info

This changes tui_gen_win_info to be allocated with new and destroyed
with delete.

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

	* tui/tui-layout.c (init_and_make_win): Use new.
	* tui/tui-data.h (struct tui_gen_win_info): Add constructor,
	destructor, initializers.
	(tui_alloc_generic_win_info): Don't declare.
	* tui/tui-data.c (_locator): Add argument to constructor.
	(source_win, disasm_win): New globals.
	(exec_info): Remove.
	(tui_source_exec_info_win_ptr, tui_disassem_exec_info_win_ptr):
	Update.
	(tui_alloc_generic_win_info): Remove.
	(init_content_element): Use new.
	(tui_win_info::tui_win_info): Update.
	(free_content_elements) <case DATA_WIN>: Use delete.