Silence a good bunch of Intel warnings

Note that some pawns and material info has been switched
to int from int8_t.

This is a waste of space but it is not clear if we have a
faster or slower code (or nothing changed), some test should be
needed.

Few warnings still are alive.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/bitbase.cpp

@@ -89,7 +89,7 @@ void generate_kpk_bitbase(uint8_t bitbase[]) {
   int i, j, b;
   for(i = 0; i < 24576; i++) {
     for(b = 0, j = 0; j < 8; b |= (compress_result(Bitbase[8*i+j]) << j), j++);
-    bitbase[i] = b;
+    bitbase[i] = (uint8_t)b;
   }
 
   // Release allocated memory: