py3: define xrange for python3

this is done in files where the xrange is used.
replace this with range once python2 is not supported anymore.
issue 0000995

src/Mod/Arch/Dice3DS/dom3ds.py

@@ -20,6 +20,9 @@ import os, sys, struct
 
 import numpy
 
+# xrange is not available in python3
+if sys.version_info.major >= 3:
+    xrange = range
 
 # Exceptions
 

src/Mod/Arch/Dice3DS/util.py

@@ -7,7 +7,11 @@ Defines some routines for calculating normals and transforming points.
 """
 
 import numpy
+import sys
 
+# xrange is not available in python3
+if sys.version_info.major >= 3:
+    xrange = range
 
 # Can push numpy.float64 (or even numpy.float80) into this if you
 # would like to use higher precision when calculating; results will be