Revert "Score extractors"

Are broken for big-endian case and
I have verified with MSVC 2013 Premium
bench is correct and there is no
miscompilation, so the main reason
to change the original code drops.

No functional change.

src/types.h

@@ -267,28 +267,17 @@ enum Score {
   SCORE_ENSURE_INTEGER_SIZE_N = INT_MIN
 };
 
-typedef union {
-  uint32_t full;
-  struct { int16_t eg, mg; } half;
-} ScoreView;
-
-inline Score make_score(int mg, int eg) {
-  ScoreView v;
-  v.half.mg = (int16_t)(mg - (uint16_t(eg) >> 15));
-  v.half.eg = (int16_t)eg;
-  return Score(v.full);
-}
+inline Score make_score(int mg, int eg) { return Score((mg << 16) + eg); }
 
+/// Extracting the signed lower and upper 16 bits is not so trivial because
+/// according to the standard a simple cast to short is implementation defined
+/// and so is a right shift of a signed integer.
 inline Value mg_value(Score s) {
-  ScoreView v;
-  v.full = s;
-  return Value(v.half.mg + (uint16_t(v.half.eg) >> 15));
+  return Value(((s + 0x8000) & ~0xffff) / 0x10000);
 }
 
 inline Value eg_value(Score s) {
-  ScoreView v;
-  v.full = s;
-  return Value(v.half.eg);
+  return Value((int)(unsigned(s) & 0x7FFFU) - (int)(unsigned(s) & 0x8000U));
 }
 
 #define ENABLE_BASE_OPERATORS_ON(T)                                         \