chore(cil2smt2): update Makefile
feat(cil2smt2): use cmd-line option/parsing
chore: move .merlin
tests(cil2smt2): add more tests
fix(cil2smt2): disable dumpfile
fix(cil2smt2): make unique "not now" message
fix(cil2smt2): fix a bug in handling "if-then-else"
feat(cil2smt2): add smt2.ml
feat(cil2smt2): print out smt2 header and footer
feat(cil2smt2): add var_decls in output