Install zlib shared objects on Cygwin

Imported from <a href="http://trac.sagemath.org/sage_trac/ticket/13914">trac #13914</a>.

Spkg diff, for review only.

Reported by: jpflori

Component: packages

CC: kcrisman,, dimpase

Report Upstream: N/A

Authors: Jean-Pierre Flori

Dependencies: 

Work issues: 

Reviewers: Dmitrii Pasechnik

Merged in: sage-5.7.beta4

Attachments: <ol><li><a href="http://trac.sagemath.org/sage_trac/attachment/ticket/13914/zlib-1.2.6.p0.diff">zlib-1.2.6.p0.diff: Spkg diff, for review only.</a> by jpflori at 20130114T19:53:39</li></ol>