[Windows] cpathCanonicalise: doesn't set length correctly

[BraedonWooding]

cpath/cpath.h

Line 1064 in ff6bfae

path->len = size;

Sets the input path.

Also I'm not entirely sure why we are handling the case of non-restrict, I doubt that'll apply to both windows & linux so we can likely skip a copy on one of those cases.

Likely other places too.