add fork watchers

gevent/core_.pyx

@@ -356,6 +356,9 @@ cdef public class loop [object PyGeventLoopObject, type PyGeventLoop_Type]:
     cpdef prepare(self):
         return prepare(self)
 
+    cpdef fork(self):
+        return fork(self)
+
     cpdef callback(self):
         return callback(self)
 
@@ -575,6 +578,13 @@ cdef public class prepare(watcher) [object PyGeventPrepareObject, type PyGeventP
     INIT(prepare)
 
 
+cdef public class fork(watcher) [object PyGeventForkObject, type PyGeventFork_Type]:
+
+    WATCHER(fork)
+
+    INIT(fork)
+
+
 cdef public class callback(watcher) [object PyGeventCallbackObject, type PyGeventCallback_Type]:
     """Pseudo-watcher used to execute a callback in the loop as soon as possible."""
 

setup.py

@@ -31,7 +31,6 @@ if libev_embed:
                 # libev watchers that we don't use currently:
                 ('EV_STAT_ENABLE', '0'),
                 ('EV_CHECK_ENABLE', '0'),
-                ('EV_FORK_ENABLE', '0'),
                 ('EV_CLEANUP_ENABLE', '0'),
                 ('EV_EMBED_ENABLE', '0'),
                 ('EV_ASYNC_ENABLE', '0'),