Made explicit how the end of methods is handled when replaying them.
Also, some basic pretty printing support.
Cleaned up some of the public variables in IL. 

Also added starting point for optimizng plans that aren't meant to be
used as libraries.
Created a new way of compiling the regression tests, essentially using
the command line tool just like everything else does.
Added non-library optimization, removing library code for plans without
top level interfaces.