Fix decoding of base64. We got the length wrong when the result was not

an exact multiple of 3.

I also wrote a torture test and it survived some minutes of random stuff
coded/decoded up to 16 MB data. But that would be a bit too embarassing to
commit... :-)

Volker

source/lib/util_str.c

@@ -1838,6 +1838,8 @@ DATA_BLOB base64_decode_data_blob(const char *s)
 		s++; i++;
 	}
 
+	if (*s == '=') n -= 1;
+
 	/* fix up length */
 	decoded.length = n;
 	return decoded;