Rename squares_aligned()

Rename to the shorter but still
clear aligned()

No functional change.

src/bitboard.h

@@ -223,10 +223,10 @@ inline Bitboard squares_of_color(Square s) {
 }
 
 
-/// squares_aligned() returns true if the squares s1, s2 and s3 are aligned
+/// aligned() returns true if the squares s1, s2 and s3 are aligned
 /// either on a straight or on a diagonal line.
 
-inline bool squares_aligned(Square s1, Square s2, Square s3) {
+inline bool aligned(Square s1, Square s2, Square s3) {
   return LineBB[s1][s2] & s3;
 }