fix(cil2smt2): use get_low_nbits instead of -bit
fix(cil2smt2): use Errormsg.error
chore(cil2smt2/test): use gcc as CC
fix(cil2smt2): update info output format
fix(cil2smt2): use extract_[EF]_exn to avoid unexhaustive pattern matching warnings
fix(cil2smt2/main): switch default values of lb and ub
feat(cil2smt2): take lb/ub of argument from cmd-line
chore(cil2smt2/_oasis): rename project name