Bug 107968

It appears that in the OSL code that we do some sanity checking for Unix system paths and converts double slashes (//) to a single slash. This is actually correct behaviour (except for beginning with double slashes - see bug 107967), but we haven't quite got this behaviour correct. 

POSIX actually doesn't mandate double-slashes be replaced by a single slash, it actually states that multiple slashes should be replaced with a single slash when parsing a system directory. We currently only check if there is a double-slash, which means that /path//to/file.txt becomes /path/to/file.txt but /path////to/file.txt becomes /path//to/file.txt

This shouldn't cause too many issues, however it causes us to also make ////path/to/file.txt to change to //path/to/file.txt instead of /path/to/file.txt - and that *is* wrong and problematic behaviour because POSIX treats a leading double-slash specially.