The line hight for the dialog box was not high enough; changed it from 8
to 10.

Had an embarrassing thinko in the assembler generation for the iOS
simulator, had forgotten the $ for a literal number. While at it, make
also the simulator read-only code snippet data structures
position-independent. Some minor comment improvements. Bridge seems to
work now on simulator.

Compiles, but I obviously have no idea how it works yet.

Yes, eventually we should factor out common parts from the iOS and
MacOSX code.

The dialog for the export to PDF was enhanced with a section for the
option of setting a watermark. The dialog has now a special subsection
for this with a box to insert a string for the watermark.