Comment 2 for bug 440429

Note: There is no longer a ld_ctor instruction. It has been replaced by ld_ctorsym (for constructor symbols/constants) and new_closure (for constructor functions). Clearly, constructor function names should no longer be atoms (as we always treat access to global objects with an explicit instruction now). But constructor symbols might be good candidates for atoms.

Therefore, let an atom refer to an integer or constructor symbol name (not a function), and replace the ld_intlit and ld_ctorsym instructions.