Code review comment for lp:~bialix/bzr/no-single-quote-on-win32

I think this is the right policy change.

Messing around a little with double quotes is fine: they aren't valid in filenames anyway, but single quotes are.

If the parsing is pared back to CommandLineToArgv-plus-remembering-if-it-was-quoted, UnicodeShlex could be further simplified.