Mod: Open header files with `io.open` for Python 2/3 compatibility.

modules/python/src2/hdr_parser.py

 #!/usr/bin/env python
 
 from __future__ import print_function
-import os, sys, re, string
+import os, sys, re, string, io
 
 # the list only for debugging. The real list, used in the real OpenCV build, is specified in CMakeLists.txt
 opencv_hdr_list = [
@@ -734,7 +734,7 @@ class CppHeaderParser(object):
         """
         self.hname = hname
         decls = []
-        f = open(hname, "rt")
+        f = io.open(hname, 'rt', encoding='utf-8')
         linelist = list(f.readlines())
         f.close()