Update: Emacs 24.3 has been released with full support for this new setting!
In the current trunk of emacs, you can simply customize the variable create-lockfiles:
C-h v create-lockfiles
Documentation:
Non-nil means use lockfiles to avoid editing collisions.
In your init file, you can set
(setq create-lockfiles nil)
Get it via
bzr branch bzr://bzr.savannah.gnu.org/emacs/trunk emacs-trunk
make
src/emacs
(I found out about this, because I decided to get active and just add an option like that myself… 🙂 )