fix(cil2smt2/test/test5.c): add sincostbl
fix(cil2smt2/basic.ml): increase precision in formatting float num
refactor(cil2smt2): move global vars upfront; clean up
feat(cil2smt2): add skeletal for call handler
feat(cil2smt2): filter out certain functions from translation

 - main, get_low_nbit
feat(cil2smt2): int variable ``x`` gets |sin(pi * x)| <= eps
fix(cil2smt2): remove debug msg
test(cil2smt2): add test7.c
fix(cil2smt2): fix wrong pattern matching for type
refactor(cil2smt2): remove unused functions
test(cil2smt2): update test7.c
feat(cil2smt2): add cmd-line options for [lb, ub]