Partially revert the WIN32 changes

Feel free to open a new PR to add them back

Author: fantix

uvloop/includes/system.h

@@ -1,9 +1,13 @@
 from libc.stdint cimport int8_t, uint64_t
 
-cdef extern from "includes/system.h":
-    int ntohl(int) nogil
-    int htonl(int) nogil
-    int ntohs(int) nogil
+cdef extern from "arpa/inet.h" nogil:
+
+    int ntohl(int)
+    int htonl(int)
+    int ntohs(int)
+
+
+cdef extern from "sys/socket.h" nogil:
 
     struct sockaddr:
         unsigned short sa_family