Use portable python shebangs

* In conda or Gentoo Prefix, we don't want to use the system python and
  instead rely on PATH lookup.

genUnicode.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python -u
+#!/usr/bin/env python
 #
 # Original script modified in November 2003 to take advantage of
 # the character-validation range routines, and updated to the