enable cmdline offscreen rendering with win64- fix ambiguous unicode stu...

win64 had an issue where it failed to render from commandline to .png files. 

this is a fix for that. it just makes it explicit that we are dealing with windows unicode w-char functions and L"strings". 

printing of windows errorcodes also have been added

32bit and 64bit have been tested under 64-bit windows. 

fix issue #387