Namelist of Twenex subdirectories

[MACRAKIS at USC-ISIE]

Since the Car part of Namelist is supposed to represent the device/directory
hierarchy, I should think that a Twenex filename of the form a:<b.c>d.e should
correspond to a namelist of ((a b c) d e) and not ((a |b.c|) d e).
Currently, namelists like ((a b c) d e) are neither accepted as legal nor
produced.  Note that Twenex allows arbitrarily many levels of subdirectories in
general.