Use prefix operators wherever possible

No functional change.
Use double everywhere

Rationale:

- Speed of double and float is about the same (not on the hot path anyway)

- Double makes code prettier (no need to write 1.0f, just 1.0)

- Only practical advantage of float is to use less memory, but since we never
  store large arrays of double, we don't care.

No functional change.
Use TT refined value to stand pat

Passed both short TC:
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 17811 W: 3520 L: 3366 D: 10925

And long TC:
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 30255 W: 5070 L: 4825 D: 20360

bench: 8340585
Increase slowmover and reduce instability

These two changes go in opposite directions and it
seems that the combination is stronger than original.

Here are the positive tests at various TC:

15+0.05
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 24561 W: 4946 L: 4772 D: 14843

60+0.05
LLR: 2.96 (-2.94,2.94) [0.00,6.00]
Total: 15259 W: 2598 L: 2423 D: 10238

40/30
LLR: 2.96 (-2.94,2.94) [-3.00,3.00]
Total: 2570 W: 527 L: 422 D: 1621

Unfortunately there is also a bad result
with one sec time increment that needs
to be further investigated:

12+1
LLR: -2.97 (-2.94,2.94) [-3.00,3.00]
Total: 2694 W: 438 L: 543 D: 1713

bench: 8340585
Smoother transition for LMR

Passed both short TC:
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 12376 W: 2596 L: 2454 D: 7326

And long TC:
LLR: 2.97 (-2.94,2.94) [0.00,6.00]
Total: 14798 W: 2584 L: 2409 D: 9805

bench: 8279065
Remove unuseful optimization in RKISS

Don't need a struct here. Speed test shows
result is teh same. Moreover RKISS is used
mainly at startup to compute magics, so
prefer to keep it simple...RKISS ;-)

Also some assorted triviality while there.

No functional change.
Merge remote-tracking branch 'upstream/master' into B04Alekhine