Patch from Egmont Koblinger to implement two extended variants of

Patch from Egmont Koblinger to implement two extended variants of
xterm mouse tracking, both supported by the current up-to-date xterm
(288). They take the form of two new DEC terminal modes, 1006 and
1015, which do not in themselves _enable_ mouse tracking but they
modify the escape sequences sent if mouse tracking is enabled in the
usual way.

[originally from svn r9752]