Overtyping the first half of a wide character with the
second half of a wide character results in display garbage.
This is because the trailing dummy is not cleaned up.

i.e.  ATTR_WIDE, ATTR_WDUMMY, ATTR_WDUMMY

Here is a short script for demonstrating the behavior:

	#!/bin/sh
	alias printf=/usr/bin/printf
	printf こんにちは！; sleep 2
	printf '\x1b[5D'; sleep 2
	printf へ; sleep 2
	printf ' '; sleep 2
	echo

According to the spec the argument is optional for 104, so p can be
NULL as can be tested with printf '\x1b]104\x07'. This is a regression
of 8e31030.

Otherwise the message "erresc: unknown str" is printed.

from the XmbTextListToTextProperty(3) man page:

"If insufficient memory is available for the new value string, the functions
return XNoMemory.  If the current locale is not supported, the functions return
XLocaleNotSupported.  In both of these error cases, the functions do not set
text_prop_return."

Reported by Steffen Nurpmeso <steffen@sdaoden.eu>, thanks!

In the current implementation, the slave PTY (assigned to the variable
`s') is always closed after duplicating it to file descriptors of
standard streams (0, 1, and 2).  However, when the allocated slave PTY
`s' is already one of 0, 1, or 2, this causes unexpected closing of a
standard stream.  The same problem occurs when the file descriptor of
the master PTY (the variable `m') is one of 0, 1, or 2.

In this patch, the original master PTY (m) is closed before it would
be overwritten by duplicated slave PTYs.  The original slave PTY (s)
is closed only when it is not one of the stanrad streams.

The bits of uint signal in an XKeyEvent which concern the key group (keyboard
layout) are bits 13 and 14, as documented here:
https://www.x.org/releases/X11R7.7/doc/libX11/XKB/xkblib.html#Groups_and_Shift_Levels
In the older version, only bit 13 was marked as part of XK_SWITCH_MOD, this
causes issues for users who have more than two keymaps. the 14th bit is not
in ignoremod, key sequences are not caught by match(), if they switch to a third
or fourth keyboard.

Only touch a few things, the main focus is to
improve code readability.