Fix KXK endgame

Position is win also if strong side has a bishop
and a knight (plus other material, otherwise
KBNK would be triggered instead of KXK).

This fixes a subtle bug where a search on position

k7/8/8/8/8/P7/PB6/K7 b - - 6 1

Instead of returning a draw score, suddendly returns
a big score. This happens because at one point in
search we reach this position:

8/Pk6/8/8/8/4B3/P7/K7 w - - 3 8

Where white can promote. In case of rook promotion (and also in case of
queen promotion) the resutling position gets a huge static eval that is
above VALUE_KNOWN_WIN (from the point of view of white). So for rook
promotion it is

          &&  futilityBase > -VALUE_KNOWN_WIN

that prevents futility pruning in qsearch. (Removing this condition indeed
lets the problem occur). Raising the static eval for K+B+N+X v K to a value
higher than VALUE_KNOWN_WIN fixes this particular problem without having to
introduce an extra futility pruning condition in qsearch.

I just checked and it seems K+R v K, K+2B v K and even K+B+N v K already get
a huge static eval. Why not K+B+N+P v K?

I think this fix corrects an oversight. There is special code for KBNK, but
KBNXK is handled by KXK, so the test for sufficient material should also test
for B+N.

bench: 8678654
Revert back KBPsK to latest Gary's version

The bug was found to be elsewhere. This version
is correct and also is able to detect as draw
positions like:

8/8/5b2/8/8/4k1p1/6P1/5K2 b - - 6 133

bench: 8678654
Revert stalemate detection in evaluation

Unfortunatly we have a slow down that causes
a regression in STC with no-regression mode:

LLR: -2.96 (-2.94,2.94) [-3.00,1.00]
Total: 22454 W: 3836 L: 4029 D: 14589

bench: 8678654
Revert dynamic contempt

On a final fixed game number test it failed
to prove better than standard version.

STC 15+0.05

ELO: -0.86 +-1.7 (95%) LOS: 15.8%
Total: 57578 W: 10070 L: 10213 D: 37295

bench: 8802105
Change search() signature

Pass SpNode as template parameter.

No functional change.