I've put the ubiqx headers back into includes.h, and removed them from

I've put the ubiqx headers back into includes.h, and removed them from
dir.c & mangle.c.  This was possible after I checked the tree code to make
sure that the tree code did not reference functions by macro name.  Also,
note that the AVL module has been removed to prevent conflict with the
SplayTree macro defines.

Chris -)-----