Calling with a new stack, with a runtime-known stack pointer (e.g.
not a global variable) is regressed with this branch. It is now a
compile-error, due to the Runtime Hint system not being smart enough
to mix a compile-time modifier field with a runtime stack field.
I'm OK with this regression because this feature is flawed (see #3268)
and may be deleted from the language.
656cc33f8d