We have utmp with utempter now and that's the best we're going to get.
Notes for better mouse support.
Merge branch 'master' of ssh://git.code.sf.net/p/tmux/tmux-code
FAQ:  Mention Git before filing bug reports

It's tedious having to tell people all the time to try the Git version to
see if a given problem is reproducible; put this in the FAQ and hope people
read it.