Patch #555929: Cygwin AH_BOTTOM cleanup patch

This patch complies with the following request found
near the top of configure.in:

# This is for stuff that absolutely must end up in pyconfig.h.
# Please use pyport.h instead, if possible.

I tested this patch under Cygwin, Win32, and Red
Hat Linux. Python built and ran successfully on
each of these platforms.
diff --git a/Include/pyport.h b/Include/pyport.h
index 790c7af..5c3e0a9 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -384,9 +384,19 @@
 extern double hypot(double, double);
 #endif
 
+#ifndef __CYGWIN__
 #ifndef DL_IMPORT       /* declarations for DLL import */
 #define DL_IMPORT(RTYPE) RTYPE
 #endif
+#else /* __CYGWIN__ */
+#ifdef USE_DL_IMPORT
+#define DL_IMPORT(RTYPE) __declspec(dllimport) RTYPE
+#define DL_EXPORT(RTYPE) __declspec(dllexport) RTYPE
+#else /* !USE_DL_IMPORT */
+#define DL_IMPORT(RTYPE) __declspec(dllexport) RTYPE
+#define DL_EXPORT(RTYPE) __declspec(dllexport) RTYPE
+#endif /* USE_DL_IMPORT */
+#endif /* __CYGWIN__ */
 
 /* If the fd manipulation macros aren't defined,
    here is a set that should do the job */