devel

Careful, first line matters.

The purpose of this file is to control whether the Makefile compiles a
devel or a release build.  If it doesn't exist, a release build is
compiled.  Therefore upon release I don't have to edit any files to
change development defaults, I can just exclude this file from the
tarball.

If you found this file in a release tarball, well, obviously somebody
else messed up.
