Allow multiple circuit modifiers

[jmbr]

Unlike with regular gates, it is not currently possible to apply multiple modifiers to a circuit. For instance, the expansions

DEFCIRCUIT FOOBAR q0 q1:
    X q0; Z q1

DAGGER DAGGER FOOBAR 0 1
CONTROLLED DAGGER FOOBAR 2 0 1
CONTROLLED CONTROLLED FOOBAR 3 2 0 1
FORKED ...

will fail.