+/// The TTEntry class is the class of transposition table entries
+///
+/// A TTEntry needs 128 bits to be stored
+///
+/// bit 0-63: key
+/// bit 64-95: data
+/// bit 96-111: value
+/// bit 112-127: depth
+///
+/// the 32 bits of the data field are so defined
+///
+/// bit 0-16: move
+/// bit 17: stored value equals static value
+/// bit 18-19: not used
+/// bit 20-22: value type
+/// bit 23-31: generation