python: Better sort dictionary keys/values

In Python 2, dict.keys() and dict.values() both return a list, which can
be sorted in two ways:

* l.sort() modifies the list in-place;
* sorted(l) returns a new, sorted list;

In Python 3, dict.keys() and dict.values() do not return lists any more,
but iterators. Iterators do not have a .sort() method.

This commit moves the build scripts to using sorted() on dict keys and
values, which makes them compatible with both Python 2 and Python 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

@@ -391,8 +391,7 @@ static const struct proc_pair
    const char *name;
    _glapi_proc proc;
 } proc_pairs[%d] = {""" % len(procs))
-        names = procs.keys()
-        names.sort()
+        names = sorted(procs.keys())
         for i in xrange(len(names)):
             comma = ',' if i < len(names) - 1 else ''
             print('   { "%s", (_glapi_proc) gl%s }%s' % (names[i], procs[names[i]], comma))