Style disassembly in the TUI

Style disassembly in the TUI

This patch changes the TUI disassembly window to style its contents.
The styling should be identical to what is seen in the CLI.  This
involved a bit of rearrangement, so that the source and disassembly
windows could share both the copy_source_line utility function, and
the ability to react to changes in "set style enabled".

This version introduces a new function to strip the styling from the
address string when computing the length.  As a byproduct, it also
removes the unused "insn_size" computation from
tui_disasm_window::set_contents.

gdb/ChangeLog
2019-11-05  Tom Tromey  <tom@tromey.com>

	* tui/tui-source.h (struct tui_source_window): Inline
	constructor.  Remove destructor.
	<style_changed, m_observable>: Move to superclass.
	* tui/tui-winsource.h (tui_copy_source_line): Declare.
	(struct tui_source_window_base): Move private members to end.
	<style_changed, m_observable>: Move from tui_source_window.
	* tui/tui-winsource.c (tui_copy_source_line): Move from
	tui-source.c.  Rename from copy_source_line.  Add special handling
	for negative line number.
	(tui_source_window_base::style_changed): Move from
	tui_source_window.
	(tui_source_window_base): Register observer.
	(~tui_source_window_base): New.
	* tui/tui-source.c (copy_source_line): Move to tui-winsource.c;
	rename.
	(tui_source_window::set_contents): Use tui_copy_source_line.
	(tui_source_window::tui_source_window): Move to tui-source.h.
	(tui_source_window::~tui_source_window): Remove.
	(tui_source_window::style_changed): Move to superclass.
	* tui/tui-disasm.c (tui_disassemble): Create string file with
	styling, when possible.  Add "addr_size" parameter.
	(tui_disasm_window::set_contents): Use tui_copy_source_line.
	Don't compute maximum size.
	(len_without_escapes): New function

Change-Id: I8722635eeecbbb1633d943a65b856404c2d467b0