[runtime] Add %ToString and %_ToString and remove the TO_STRING builtin.

src/ia32/interface-descriptors-ia32.cc

Index: src/ia32/interface-descriptors-ia32.cc
diff --git a/src/ia32/interface-descriptors-ia32.cc b/src/ia32/interface-descriptors-ia32.cc
index 107e6290d2d2497b519544a97bbea98c0ebb4786..1c0402f11767e427403e73b99cdb314db1a6c5cc 100644
--- a/src/ia32/interface-descriptors-ia32.cc
+++ b/src/ia32/interface-descriptors-ia32.cc
@@ -107,6 +107,10 @@ void ToNumberDescriptor::InitializePlatformSpecific(
 
 
 // static
+const Register ToStringDescriptor::ReceiverRegister() { return eax; }
+
+
+// static
 const Register ToObjectDescriptor::ReceiverRegister() { return eax; }