python: Use range() instead of xrange()

Python 2 has a range() function which returns a list, and an xrange()
one which returns an iterator.

Python 3 lost the function returning a list, and renamed the function
returning an iterator as range().

As a result, using range() makes the scripts compatible with both Python
versions 2 and 3.

Signed-off-by: Mathieu Bridon <bochecha@daitauha.fr>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mapi/glapi/gen/glX_proto_send.py

@@ -392,7 +392,7 @@ static const struct proc_pair
    _glapi_proc proc;
 } proc_pairs[%d] = {""" % len(procs))
         names = sorted(procs.keys())
-        for i in xrange(len(names)):
+        for i in range(len(names)):
             comma = ',' if i < len(names) - 1 else ''
             print('   { "%s", (_glapi_proc) gl%s }%s' % (names[i], procs[names[i]], comma))
         print("""};