Define the child callback on win32, needed to link.

CHANGES.rst

@@ -249,7 +249,7 @@ libev
 
 - The C extension has been updated to use more modern Cython idioms
   and generate less code for simplicity, faster compilation and better
-  cache usage.
+  cache usage. See :issue:`1076`.
 
 - The ``sigfd`` property that was only conditionally available on
   certain platforms and when libev was embedded, and only in the C

src/gevent/libev/callbacks.h

@@ -11,21 +11,12 @@
     DEFINE_CALLBACK(check, Check);     \
     DEFINE_CALLBACK(fork, Fork);       \
     DEFINE_CALLBACK(async, Async);     \
-    DEFINE_CALLBACK(stat, Stat);
+    DEFINE_CALLBACK(stat, Stat);       \
+    DEFINE_CALLBACK(child, Child);
 
 
-#ifndef _WIN32
-
-#define DEFINE_CALLBACKS               \
-    DEFINE_CALLBACKS0                  \
-    DEFINE_CALLBACK(child, Child)
-
-#else
-
 #define DEFINE_CALLBACKS DEFINE_CALLBACKS0
 
-#endif
-
 
 DEFINE_CALLBACKS