Type Buffer's flags argument (#648)

numcodecs/compat_ext.pyx

@@ -12,7 +12,7 @@ from .compat import ensure_contiguous_ndarray
 cdef class Buffer:
     """Convenience class for buffer interface."""
 
-    def __cinit__(self, obj, flags):
+    def __cinit__(self, obj, int flags):
         PyObject_GetBuffer(obj, &(self.buffer), flags)
         self.acquired = True
         self.ptr = <char *> self.buffer.buf