[runtime] Remove unused TO_NUMBER and TO_STRING functions.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index 231e83283c04d02f28f74e4ce6202a09ece40bc0..8063a790e131f9c169b15bab728dfa7462c29a71 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -605,18 +605,6 @@ function STACK_OVERFLOW(length) {
 }
 
 
-// Convert the receiver to a number - forward to ToNumber.
-function TO_NUMBER() {
-  return %to_number_fun(this);
-}
-
-
-// Convert the receiver to a string - forward to ToString.
-function TO_STRING() {
-  return %to_string_fun(this);
-}
-
-
 /* -------------------------------------
    - - -   C o n v e r s i o n s   - - -
    -------------------------------------