Add Cython patch for Cygwin

Author: jdemeyer

build/pkgs/cython/package-version.txt

@@ -1 +1 @@
-0.25.2.p1
+0.25.2.p2

build/pkgs/cython/patches/cdef_public_dll_linkage.patch

@@ -0,0 +1,32 @@
+Patch for https://github.com/cython/cython/pull/1687
+Only needed for Cygwin systems
+
+commit 632f18f2710eaf6ee2b3a3aaa0749c7886299e64
+Author: Jeroen Demeyer <[email protected]>
+Date:   Thu Apr 27 17:13:39 2017 +0200
+
+    Do not use special dll linkage for "cdef public" functions
+
+diff --git a/Cython/Compiler/ModuleNode.py b/Cython/Compiler/ModuleNode.py
+index 6356e78..76fe4e5 100644
+--- a/Cython/Compiler/ModuleNode.py
++++ b/Cython/Compiler/ModuleNode.py
+@@ -214,8 +214,7 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
+     def generate_public_declaration(self, entry, h_code, i_code):
+         h_code.putln("%s %s;" % (
+             Naming.extern_c_macro,
+-            entry.type.declaration_code(
+-                entry.cname, dll_linkage="DL_IMPORT")))
++            entry.type.declaration_code(entry.cname)))
+         if i_code:
+             i_code.putln("cdef extern %s" % (
+                 entry.type.declaration_code(entry.cname, pyrex=1)))
+@@ -2849,7 +2848,7 @@ def generate_cfunction_declaration(entry, env, code, definition):
+             dll_linkage = "DL_IMPORT"
+         elif entry.visibility == 'public':
+             storage_class = Naming.extern_c_macro
+-            dll_linkage = "DL_EXPORT"
++            dll_linkage = None
+         elif entry.visibility == 'private':
+             storage_class = "static"
+             dll_linkage = None