Currently when you run |mach reftest| it parses the commandline into a dictionary, then reconverts that dictionary back into a command line string, then calls `make reftest` with it. This is.. erm, not ideal. It's making it hard for me to test out the reftest structured log integration. Might as well fix it first I guess.

I have a fix for this, which I almost managed to land this morning before being backed out :)

Man, I should file bugs more often.. it seems every time I do you comment saying you have a fix :p. Feel free to dupe this if you already have something else.