Implemented the Word64Popcnt TurboFan operator for x64.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index 5c021270b83682f64180b44c38f59e853c61d990..d66c9d22581adf5b88c3972835bb09d07e6cd298 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -1961,6 +1961,9 @@ Type* Typer::Visitor::TypeWord64Clz(Node* node) { return Type::Internal(); }
 Type* Typer::Visitor::TypeWord64Ctz(Node* node) { return Type::Internal(); }
 
 
+Type* Typer::Visitor::TypeWord64Popcnt(Node* node) { return Type::Internal(); }
+
+
 Type* Typer::Visitor::TypeWord64Equal(Node* node) { return Type::Boolean(); }