Ruby: Simplify SLICC and Entry/TBE handling.

Ruby: Simplify SLICC and Entry/TBE handling.
Before this changeset, all local variables of type Entry and TBE were considered
to be pointers, but an immediate use of said variables would not be automatically
deferenced in SLICC-generated code.  Instead, deferences occurred when such
variables were passed to functions, and were automatically dereferenced in
the bodies of the functions (e.g. the implicitly passed cache_entry).

This is a more general way to do it, which leaves in place the
assumption that parameters to functions and local variables of type AbstractCacheEntry
and TBE are always pointers, but instead of dereferencing to access member variables
on a contextual basis, the dereferencing automatically occurs on a type basis at the
moment a member is being accessed.  So, now, things you can do that you couldn't before
include:

Entry foo := getCacheEntry(address);
cache_entry.DataBlk := foo.DataBlk;

or

cache_entry.DataBlk := getCacheEntry(address).DataBlk;

or even

cache_entry.DataBlk := static_cast(Entry, pointer, cache.lookup(address)).DataBlk;