ninja windows: internal cleanup, get rid of self.configname
ninja windows: internal cleanup, get rid of self.configname

It was pseudo-global, kind of weird, and better off gone. I don't think I'll miss him.

R=thakis@chromium.org

Review URL: https://chromiumcodereview.appspot.com/9965001
witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp