X87: Added Popcnt as an optional operator and implement it on x64 and ia32.

src/x87/macro-assembler-x87.h

Index: src/x87/macro-assembler-x87.h
diff --git a/src/x87/macro-assembler-x87.h b/src/x87/macro-assembler-x87.h
index ecbb4f59c64530b4a72cf2ed48faffbd694f00d3..5a1f0cbb15630da71c25e54f4d2b92a679977804 100644
--- a/src/x87/macro-assembler-x87.h
+++ b/src/x87/macro-assembler-x87.h
@@ -812,6 +812,9 @@ class MacroAssembler: public Assembler {
   void Tzcnt(Register dst, Register src) { Tzcnt(dst, Operand(src)); }
   void Tzcnt(Register dst, const Operand& src);
 
+  void Popcnt(Register dst, Register src) { Popcnt(dst, Operand(src)); }
+  void Popcnt(Register dst, const Operand& src);
+
   // Emit call to the code we are currently generating.
   void CallSelf() {
     Handle<Code> self(reinterpret_cast<Code**>(CodeObject().location()));