Make show less painful and awful. Some comments updated.

This was done to prepare it to be called from a function. Also, o_new_instance
and o_get_function now work properly in show.

I decided to use a giant table to hold all opcode information. The opcode is
at the front of each entry so that it can easily be sanity-checked by looping
over the opcode table and checking opcode_table[i][0] == i.

I tried splitting show off into functions, only to be horrified at the mess
that resulted and backtracking on it. So I'll just make show into a function.
show is now a function, not an opcode. Some debug comments touched up too.

I've decided to turn this into a function since I'd rather have things be
functions instead of keywords. I'll later remove isnil once the Maybe class
finally comes (though that will be a long time, I think).
Show now nicely dumps instance values. Fixes #56.

It now prints the name of the property (as well as where it inherited from),
but doesn't print a tag if it's just the current class.

For a Point class with no parent, the properties are simply printed.
For a ValueError class (which has Exception as a parent), properties are
listed as being inherited from Exception.

This code has a bug, however: If a class has properties and the parent does,
all properties will be printed under the parent. I intend to leave this in
until classes are more stable (so I don't have to redo the fix if properties
change or somesuch).

Oh, and user-defined classes are printed backwards. Whoops!