[turbofan] Turn Math.clz32 into an inlinable builtin.

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 1eb7f6effefc7c32bbc6ae96ad6f25bb5e80c68a..8db4df346c7f51d36ad20e46b784c6e94ed0134f 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -927,6 +927,9 @@ class MacroAssembler: public Assembler {
   void Pinsrd(XMMRegister dst, Register src, int8_t imm8);
   void Pinsrd(XMMRegister dst, const Operand& src, int8_t imm8);
 
+  void Lzcntl(Register dst, Register src);
+  void Lzcntl(Register dst, const Operand& src);
+
   // Non-x64 instructions.
   // Push/pop all general purpose registers.
   // Does not push rsp/rbp nor any of the assembler's special purpose registers