XSB Src (SVN)-old

Adding more subsumptive, incremental tests.

New tests for subsumptive + incremental. I had to make a few minor changes, so I did this rather than using the -S option.

typo fix

elseif--> elif in conditional compillation
in prolog-commons/c_arith, replaced succ/2 with a correct definiion

Updated manual to removed incompataibility of subsumptive and incremental (yay!) I'll update the rest of the code soon.
Also took out a number of references to the multi-threaded engine which is no longer supported (sign)

Init c to NULL to be sure always defined.

Last one, I hope!

A bit of spaghetti effect -- need to support a different arity of a call .

Some define statements needed for the iter_sub_trie_lookup switch.

Fixed bug with WFS and call subsumption. Call subsumption uses the same routines for adding calls and answers.
Therefore if there is an answer p(X), an answer p(1) will not be added. This if fine if all answers are unconditional, but
not if the answers are conditional. For instance if there is an answer p(X) <- undefined, we still want to add an unconditional answer p(1).
This wasn't happening, so I put a switch in iter_sub_trie_lookup to do a variant check when adding answers but (of course) maintaining its subsumption
check for calls.

I found this case when working on call subsumption and incremental tabling, so there is an ifdef or two for incremental tabling, but it wont hurt anything, I hope.