6 character external identifiers

[DBrown at HI-MULTICS.ARPA]

  A nice canonizer (canonical-izer) is the following:
  while (too long and not at the first character)
     wipe out "_"s from right to left
     wipe out vowels from right to left
  truncate at N characters

  This tends to produce recognizable abbreviations for names in the 6-15
character range.  After that, all bets are off!
  --dave