readFilename: only recognise '\"' and '\ ' as being escaped; '\<any other char>' is now processed as two chars.
readFilename: only recognise '\"' and '\ ' as being escaped;
'\<any other char>' is now processed as two chars.

This change is an attempt to improve the handling of options /
filenames that contain single backslashes (cf. steady trickle of
Winhugs bug reports due to Registry options inadvertently
(or not) containing non-escaped backslashes.)

I've yet to convince myself fully that its worth the risk
of including this change in the upcoming release, so I may
end up disabling the code (after having slept on it.)

FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs