Fix compilation on x64.

TBR=ager@chromium.org

Review URL: http://codereview.chromium.org/5873003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6036 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/full-codegen-x64.cc

@@ -199,7 +199,7 @@ void FullCodeGenerator::Generate(CompilationInfo* info) {
 
 
 void FullCodeGenerator::ClearAccumulator() {
-  __ xor(rax, rax);
+  __ xor_(rax, rax);
 }