Add perft 'divide' command

To show perft numbers for each move. Just
use 'divide' instead of 'perft', for instance:

position startpos moves e2e4 e7e5
divide 4

Inspired by Ronald de Man.

No functional change.
Tidy up tt.h

Backport some non-functional changes
found working on 'dense TT' patch.

No functional change.
Fix a warning with Intel compiler

warning #2259: non-pointer conversion from
"int" to "int16_t={short}" may lose significant
bits.

No functional change.
Revert "Symmetric king safety"

Regression test of 40K games at 60 secs shows
this commit to be a 2-3 ELO regression.

So revert to original king safety.

bench: 8732553
Stockfish 5

Stockfish bench signature is: 8732553
Restore development version

bench: 8732553
Retire polyglot.ini

All actively maintained GUI are able
to understand UCI protocol, so there
is no more need for this obsolete file.

No functional change.
Retire eval weights UCI options

There is really little that user can achieve (apart
from a weakened engine) tweaking these parameters
that are already tuned and have no immediate or visible
effect.

So better do not expose them to the user and avoid the
typical "What is the best setup for my machine?" kind of
question (by far the most common, by far the most useless).

No functional change.
Retire Polyglot Book management

Book handling belongs to GUI, we kept this code
for historical reasons, but nowdays there is
really no need of this old, (mostly) unused
and especially incorrect designed functionality.

It is up to the GUI to choose the book (far easier for
the user) and to select the book parameters. In no
place, including fishtest, TCEC, rating lists, etc.
the "own book" is used, moreover currently SF is
released without any book and even if in the future we
bundle a book in the release package, it will be the GUI
that will take care of it.

This corrects a wrong design decision that Galurung
and later Stockfish inherited from what was common
practice many yeas ago.

No functional change.