Remove obsolete code to handle Hebrew and Arabic characters

Remove obsolete code to handle Hebrew and Arabic characters

This is handled by Qt now.

Note that a small optimization (do not draw text that is to the left
of WorkArea) is removed because it cannot be guaranteed to be exact
anymore. It was probably not very useful anyway, and would become
useless once the RowPainter is rewritten to use Row information.

Update 00README_STR_METRICS_BRANCH.