Added helper functionality to win/wb.py

Added helper functionality to win/wb.py

This change adds several helper functions to win/wb.py:

- config-win32.h parser (to read build configuration options)
- helper function to cd to service-win32 for openvpnserv.exe building
- code to dynamically generate TAP-driver -related variables from version.m4,
  required by tap-win32/tapdrv.c
- configure.h generator to allow viewing build options using openvpn --version
- creation of temporary version.m4-based file to allow importing it's variables
  to the NSI installer script (win/openvpn.nsi)
- helper function to rename files (used in win/make_dist.py)

Signed-off-by: Samuli Seppänen <samuli@openvpn.net>
Acked-by: James Yonan <james@openvpn.net>
Signed-off-by: David Sommerseth <dazo@users.sourceforge.net>