Patch #404680: disables the nis module and enables the dl module when
    building under Cygwin.  Makes some fixes to the dlmodule in order to
    compile with Cygwin.
diff --git a/setup.py b/setup.py
index 0892f16..f9524e6 100644
--- a/setup.py
+++ b/setup.py
@@ -387,12 +387,13 @@
             exts.append( Extension('dl', ['dlmodule.c']) )
             
             # Sun yellow pages. Some systems have the functions in libc.
-            if (self.compiler.find_library_file(lib_dirs, 'nsl')):
-                libs = ['nsl']
-            else:
-                libs = []
-            exts.append( Extension('nis', ['nismodule.c'],
-                                   libraries = libs) )
+            if platform not in ['cygwin']:
+                if (self.compiler.find_library_file(lib_dirs, 'nsl')):
+                    libs = ['nsl']
+                else:
+                    libs = []
+                exts.append( Extension('nis', ['nismodule.c'],
+                                       libraries = libs) )
 
         # Curses support, requring the System V version of curses, often
         # provided by the ncurses library.