Reduce penalty for doubled pawns further away from each other

Passed both STC
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 38339 W: 6849 L: 6649 D: 24841

and LTC
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 22693 W: 3455 L: 3256 D: 15982

bench: 7508468
Move LowMobPenalty into psq/mobility tables

Tested in no-regression mode.

Passed both STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 36705 W: 6537 L: 6443 D: 23725

and LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 9358 W: 1495 L: 1358 D: 6505

bench: 6921356
Big reshuffle in evaluate.cpp

Reshuffle functions to define them in reverse
calling order (C style).

This allow us to define templates before they are
used. Currently it is not like this, for instance
evaluate_pieces is defined after do_evaluate that
calls it. This happens to work for some strange
reason (two phase lookup?) but we want to avoid
code that works 'by magic'.

As a nice side-effect we can now remove the function
prototypes.

No functional change.
Add PEXT software implementation

For development/debug purposes.

No functional change.
Implement PEXT based attacks

According to:

https://chessprogramming.wikispaces.com/BMI2#PEXTBitboards

No functional change.
Switch to hardware PEXT

Retire software pext and introduce hardware
call when USE_PEXT is defined during compilation.

This is a full complete implementation of sliding
attacks using PEXT.

No functional change.
Add ARCH x86-64-bmi2 support

Intel Haswell and newer CPUs can calculate sliders
attacks using special PEXT asm instructions instead
of magic bitboards. This gives a +3% speed up.

To enable it just compile with ARCH=x86-64-bmi2

No functional change.
Retire signature-build

Does not seem used.

No functional change.
Fix a typo in evaluate

Spotted by Lyudmil Antonov.

No functional change.
Add a bonus for each eatable pawn