Define control message constants at compile time.
Make +PASS-THROUGH+ available at load-time.
Make constants in local-node.lisp available at load time.

The constants +HIGHEST-VERSION-SUPPORTED+ and
+LOWEST-VERSION-SUPPORTED+ are needed in empd.lisp at load time.
Use the actually existing function ERLANG-TERM:TUPLE-REF.
Use the general and actually exported DECODE when decoding control messages.
Package CLERIC-EPMD depends on CLERIC.
Bumped version to 0.2.1.