the line numbers are limited to unsigned short in the parser and
consequently the evaluator. as that's an internal detail that could
change any time, the display works with ints. so the special value ~0
needs to be converted to -1 in the right place.

Change-Id: Ia9437164b88ecf2077ffc4c01d7e16033970df1b
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>