XSB Src (SVN)-old

Added documentation of timed_call_modify/1 and current_timed_call/2.
Also cleaned up some indexing statements.

Added a cast to quiet compiler.

provided the incr_storage_find_... versions of the storage_find_* calls.

Added an error condition when trying to invalidate a non-incremental trie.

more initializations in the prref struct

Test for various large tabled terms -- ground and with lots of variables.

Added check for too many variables in answer -- see previous commit for details.

Added check for adding into a table an answer with a large number
of variables. The problem is that the variables get trailed, so
if there are enough variables, they will cause a TCP stack realloc, which messes up
the table choice point pointers in new_answer_dealloc.

This should be simple enough to fix, but since the limit is about
40000 variables in an answer, we should be ok for now.

Added a flag for max variables in a tabled subgoal (see previous commit message). This flag will
not need to be used, except for experimenting.

Fixed a bug in variant call search that arose when tabling a subgoal with thousands of variables. The bug arose
because some information was integer-encoded and decoded inconsistently. Also, I did a check on the maximum number
of variables in a subgoal, which I set to 2000, as a large number of variables in a subgoal will likely cause
problems somewhere else, and I think its reasonable to assume that such large subgoals are probably errors. The
exact number can be controlled by a flag, but the flag should only be used for experimentation.