Redo checkbox position extraction.

This should be a bit more acurate, as we use the exact position that
PGF knows from placing the object.
Remove compatibility stuff
New checkbox position calculation in tex

This also fixes the coordinate output. It was off by half the
line width in the x direction.
Fix up the y position output of checkboxes.
Fix size of textboxes.

They were all 0.5pt (bp) to small in every direction. This is now fixed.
Remove offinterlineskip and change some spacings.
Tweak and fix the spacings.
Add struts so that tabularx is layed out correctly.

This was a pain to debug. We need to add struts to the question as
otherwise multiline tables would move to close to the question.
We now have struts at different spots to ensure everything is layed
out correctly.
Put the page marking into the title.

This means that if someone overrides the title handling, they need
to call \sdapspagemark!
Use the footer for pagemarks and set correct font.
Add "form" attribute to checkbox.
Add masked coverage counter.
Use mask intead of fixed box border based counting.

This has two advantages:
 * The current rotation/sheer can be taken into account
 * Any form can be used.
More mask based API and usage of it.
Add support for circular checkboxes.

These are called elliptical internally, because in theory they could be
elliptical. However, the LaTeX class only has one length for both
width and height.
Add support for elliptical checkboxes to annotate and gui.
Whitespace fixes.
Move more generic functions to handle A1 surfaces to surface.c
Fix some warnings.
Add missing file, and compile it.