[htop-general] Patch for -p option

[Rob H. <ro...@ho...>]

Hello htop users and developers,

I've written a patch to add a -p option to htop, similar to top's
-p option.  For those unfamiliar with top's -p option, it allows you
to specify a set of pids to monitor, instead of every running process.

I've also attached a patch to tell MakeHeader.py to use Python 2; feel
free to disregard this if it breaks too many build environments.

Thanks,
Rob Hoelz