Support extended mouse coordinates.

Using the legacy method, mouse coordinates can be reported only up to 223. If
you have a wider terminal, you cannot use the mouse in the rightmost columns.

There exist two extensions to overcome this problem, a broken one invented by
xterm (the "DEC 1005" mode) which is supported by xterm, urxvt and iterm2; and
a good one invented by urxvt (the "DEC 1015" mode), supported by urxvt and
iterm2.

Many thanks to Egmont Koblinger for report and patch.


FIXED-IN: 4.9