Choose behavior based on the current bfr mode.
Usage:
(brf-case :aig aigcode :bdd bddcode)
expands to aigcode if we are currently in AIG mode, or bddcode if we are currently in BDD mode. This is often used to implement basic wrappers like bfr-and.
Macro: bfr-case
(defmacro bfr-case (&key aig bdd) (cons 'if (cons '(bfr-mode) (cons aig (cons bdd 'nil)))))