Eliminate return/entry compiled invocation pun.

Eliminate return/entry compiled invocation pun.

There is a small cost to this.  My hope is that it will be offset by:

1. distinguishing compiled entries from compiled return addresses, in
   order to enable...

2. using indirection for compiled entries so closures don't need
   dynamically generated code, and finally...

3. using direct instruction addresses for compiled return addresses
   so we can exploit the return stack branch predictor,

which all requires this change in order to function correctly.

No change to compiled code interface intended.