STRING<=
========

Syntax: (string<= <string1> <string2>
          :START1 <number> :END1 <number>
          :START2 <number> :END2 <number>)

This function compares (parts of) strings with
differentiation between upper- and lowercase-
characters. It returns T or the length of the common
begin-part, when the strings are equal, otherwise NIL.

example:       >(string<= "Computer" "Computer")
               T