[Exim] Exim on Cygwin

With the help of Philip, Exim now compiles out of the
box on all Windows machines, using the Cygwin emulation
layer http://sources.redhat.com/cygwin .

A precompiled port of Exim 4.01 is available on
ftp://ftp.uni-erlangen.de/pub/pc/gnuwin32/cygwin/porters/Humblet_Pierre_A/V1.1/

Pierre