c,python: Use little-endina byte order for bigint arithmetics

This better matches what one would expect from the hex or base64
(upcoming) formats.

python/passgeny/bhash.py

@@ -21,7 +21,7 @@ class Bhash:
         """
         Initialize a Bhash from a bytes object
         """
-        self.bhash = int.from_bytes(buf, byteorder='big')
+        self.bhash = int.from_bytes(buf, byteorder='little')
         self.bits_avail = len(buf) * 8
         self.bits_used = 0.0