*** truncate-string-to-width shortens a string, if necessary,<BR>
to fit within a certain number of columns.  (Of course, it does
not alter the string that you give it; it returns a new string
which contains all or just part of the existing string.)
<P>
(truncate-string-to-width STR END-COLUMN &optional START-COLUMN PADDING)
<P>
This returns the part of STR up to column END-COLUMN.
<P>
The optional argument START-COLUMN specifies the starting column.
If this is non-nil, then the first START-COLUMN columns of the string
are not included in the resulting value.
<P>
The optional argument PADDING, if non-nil, is a padding character to be added
at the beginning and end the resulting string, to extend it to exactly
WIDTH columns.  If PADDING is nil, that means do not pad; then, if STRING
is narrower than WIDTH, the value is equal to STRING.
<P>
If PADDING and START-COLUMN are both non-nil, and if there is no clean
place in STRING that corresponds to START-COLUMN (because one
character extends across that column), then the padding character
PADDING is added one or more times at the beginning of the result
string, so that its columns line up as if it really did start at
column START-COLUMN.
<P>