Slowdown caused by RDF

The new RDF code adds a function to ap_Toolbar_Functions.cpp:
ap_ToolbarGetState_CursorInSemItem. This function is called all the
time to update the toolbar state and it is called even when RDF is not
used. The function is really slow for big files; it scales linearly
with the cursor position after an initial calculation which scales
quadratically with the cursor position. The initial calculation seems
to be triggered every time the cursor is moved with the mouse. I think
that this function needs to be removed or at the very least modified
so that it does not affect people who do not use RDF. Note: I have no
idea how important it is for RDF that this calculation be done
continuously.

Simon