Send xterm mouse tracking codes

This patch provides an option to send xterm mouse tracking codes to the terminal.  When the option is enabled, and when the console application requests mouse tracking, tap events are forwarded as clicks and drag/fling events are forwarded as scroll wheel events.  Examples of applications which can be configured to accept mouse events are `vim` and `tmux`.

Currently `less` does not scroll.  Terminals such as gnome-terminal and konsole forward scroll events as cursor keys when applications are using the alternate screen buffer.  If the present patch is accepted, I plan to next implement this kludge so that `less` can scroll as well.

I have not implemented the DEC save and restore commands for the mouse tracking flags, although this probably doesn't matter.  Probably the way forward here is to use a BitSet rather than an integer to store the flags, as this will enable handling flags greater than 32 in a unified way.