Use simple array for Pawns Connected bonus #2061

Simplification which removes the pawns connected array.
Instead of storing the values in an array, the values are
calculated real-time. This is about 1.6% faster on my machines.

Performance:
master ave nps: 159,248,672
patch ave nps: 161,905,592

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 20363 W: 4579 L: 4455 D: 11329
http://tests.stockfishchess.org/tests/view/5c9925ba0ebc5925cfff79a6

Non functional change.

src/pawns.h

@@ -76,7 +76,6 @@ struct Entry {
 
 typedef HashTable<Entry, 16384> Table;
 
-void init();
 Entry* probe(const Position& pos);
 
 } // namespace Pawns