remove definitions of dummy ev_xxx_child methods

gevent/libev.h

@@ -3,13 +3,3 @@
 #else
 #include "ev.h"
 #endif
-
-#if (!EV_CHILD_ENABLE)
-/* When ev_child is not available (Windows), we should not define gevent.core.child and gevent.core.loop.child().
- * Temporarily defining no-op functions since there's no easy way to do optional methods with Cython. */
-void ev_child_start(void*, void*);
-void ev_child_start(void* a, void* b) {}
-void ev_child_stop(void*, void*);
-void ev_child_stop(void* a, void* b) {}
-#endif
-