Stockfish 6 Release Candidate 2

- Fix a compilation issue related to BMI2 PEXT instruction
- Retrieve a ponder move from TT if PV is only one move long

Bench: 8080602

No functional change

src/misc.cpp

@@ -31,7 +31,7 @@ namespace {
 
 /// Version number. If Version is left empty, then compile date in the format
 /// DD-MM-YY and show in engine_info.
-const string Version = "6 RC1";
+const string Version = "6 RC2";
 
 /// Debug counters
 int64_t hits[2], means[2];