We've always just used 0, which isn't correct if the function is going
to be used in a runtime pattern match. Now calculate correctly so that
we're explicit about which type level variables are used at runtime.
This might cause some programs to fail to compile, if they use functions
that calculate Pi types. The solution is to make those functions
explicitly 0 multiplicity. If that doesn't work, you may have been
accidentally trying to use compile-time only data at run time!
Fixes#1163
