ochre

Copperbox revision 2777.

First round of work coding the signal modifier built-ins.

Another nit with the type system - I don't properly handle that Ints could be actually ints or variables / pfields representing ints. This is another bit where embedding in Haskell has allowed me to shirk some duty I have to developing a sound type system. If I had designed a closed DSL, I would have been forced to address this short-coming much sooner.