[BUG] No way to escape SEPCHAR in split_external_path

[Stephen J. Turnbull]

Michael Sperber writes:

 > > I don't know if this is actually a bug or not, but apparently there is
 > > no way to escape the path separator character (typically ?/ on Unix,
 > > ?\\ on Windows) in split_external_path.

 > I always thought this was a general issue with this notation for paths
 > on Unix and Windows.  Does the PATH environment variable, for instance,
 > allow escaping?

If I knew, I would be telling, not asking. ;-)  

 > Anyway, this has, to my knowledge, never arisen in practice.  Is it
 > worth complicating the code for?

Probably not, but it should be documented.