[RFC] Allowing new eof whitelines while still doing whitespace trailing-space fix.

As part of a current mirroring project of a dirty upstream repo that has mixed line endings and leading/trailing whitespace issues it became apparent that the current trailing-space fixing in ws.c worked correctly, but the new_blank_lines_at_end processing in builtin-apply.c would remove the newly fixed line. Also, as noted in a previous thread, there are times when adding new whitelines at eof is a needed capability, yet the desire remains to correct other whitespace issues within the patch.

The patch in the follow-up post is an attempt to fix that. This is my first git-core patch, so please be honest but gentle. :P If the fix is of interest I'd be glad to go through the steps of making a test case and whatever else is needed.