*procedure
**
SPLITNAME
      To split a string on the first  occurance  of  a  par-
ticular character.
      pos := splitname ( prefix, ch, string, ptr )
      The  string  'string'  is split on the character 'ch',
except that all characters before that  indicated  by  'ptr'
are  ignored.  The  substring  up  to  but not including the
character 'ch ' is  put  into  'prefix'.  The  result  is  a
pointer  at  the first character after 'ch', or zero if 'ch'
is not found. If the prefix part of  the  string  is  longer
than thirty characters then those after the first thirty are
ignored.
      Examples :
      splitname ( pfx, ':', "sys:c.echo", 1 )
      pfx <- "sys"
      res <- 5
      splitname ( pfx, ':', "bsp:print/sys:boggle", 5 )
      pfx <- "print/sys"
      res <- 15


