Added internal wrapping ability.

Added internal wrapping ability.

New options:
  -wrapContinuationSequence "foo"  (default: "\\   "
  -useInternalWrap (Winboard default: false, XBoard default: true)

Note: -keepLineBreaksICS if set, prevents wrapping, usurping the
   useInternalWrap setting.  The idea is if you want to keep ICS line
   breaks, then you don't want internal wrapping.  Because of this,
   the new default for keepLineBreaksICS is now false for XBoard.