Rename futilityMargin in kingDanger in EvalInfo

This is what actually is.

A standard naming convention suggests to name a variable
with someting resembling _what_ the variable is and not
_how_ the variable is used. This normally results
in easier to read code.

No functional change.

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

src/evaluate.h

@@ -47,7 +47,7 @@ class Position;
 
 struct EvalInfo {
 
-  EvalInfo() { futilityMargin[0] = futilityMargin[1] = Value(0); }
+  EvalInfo() { kingDanger[0] = kingDanger[1] = Value(0); }
 
   // Middle game and endgame evaluations
   Score value;
@@ -95,9 +95,8 @@ struct EvalInfo {
   // Middle game and endgame mobility scores
   Score mobility;
 
-  // Extra futility margin. This is added to the standard futility margin
-  // in the quiescence search. One for each color.
-  Value futilityMargin[2];
+  // Value of the danger for the king of the given color
+  Value kingDanger[2];
 };