fix py27 on Windows

Author: jfolz

msgpack/_unpacker.pyx

@@ -29,7 +29,7 @@ cdef extern from "Python.h":
 from libc.stdlib cimport *
 from libc.string cimport *
 from libc.limits cimport *
-from libc.stdint cimport *
+ctypedef unsigned long long uint64_t
 
 from msgpack.exceptions import (
     BufferFull,