Remove the critial section in FastAvn. Boogie parser seems to be thread-safe now.
Remove the critial section in FastAvn. Boogie parser seems to be
thread-safe now.

boogie-org/corral,boogie-org/corral,boogie-org/corral,boogie-org/corral,boogie-org/corral,boogie-org/corral,boogie-org/corral