added latch and support atomic load

frontend/ail_to_coq.ml

frontend/coq_pp.ml

theories/examples/latch/latch.c

theories/examples/latch/latch.h

theories/examples/latch/latch_code.v

theories/examples/latch/latch_def.v

theories/examples/latch/latch_proof_latch_release.v

theories/examples/latch/latch_proof_latch_wait.v

theories/examples/latch/latch_spec.v

theories/lang/lang.v

theories/lang/lifting.v

theories/lithium/classes.v

theories/lithium/interpreter.v

theories/typing/atomic_bool.v

theories/typing/automation.v

theories/typing/globals.v

theories/typing/optional.v

theories/typing/own.v

theories/typing/programs.v

theories/typing/singleton.v