Streamline cygport file, avoiding use of private variable.
Don't attempt to build the cygport package unless RELEASE is set.
Refer to Cygwin's common-licenses directory for GPL-3.0 text. 


git-svn-id: http://mintty.googlecode.com/svn/trunk@1320 2782a51e-c42b-11dd-927d-974589228060