Fix win32 relative home path

Workaround for win32 behavior with overestimate required buffer size.
Additionally, now possible to skip [one preparation step](http://wiki.xbmc.org/index.php?title=HOW-TO:Compile_XBMC_for_Windows#Running.2FDebugging_XBMC_from_Visual_C.2B.2B_Express_2010) for build and run XBMC on Windows.