Add 'pkg' rule for building Cygwin package from Makefile.
Drop Cygwin-specific README, which is no longer required by the
packaging guidelines and didn't really provide any interesting 
information beyond what's now in the cygport file.
Bump copyright date in COPYING file.


git-svn-id: http://mintty.googlecode.com/svn/trunk@1319 2782a51e-c42b-11dd-927d-974589228060