Remove make_source_window and make_disasm_window

Remove make_source_window and make_disasm_window

This unifies the remaining creation and re-initialization cases for
the source and disassembly windows.  Once this is done, it's clear
that make_source_window and make_disasm_window aren't needed any more,
so remove them.

gdb/ChangeLog
2019-07-17  Tom Tromey  <tom@tromey.com>

	* tui/tui-layout.c (make_source_window, make_disasm_window):
	Remove.
	(show_data): Unify creation and re-initialization cases.