enhance queue in LibUtil
add signature file for LibUtil
add type annotations
add type annotations and singatures for LibUtil
more meaningful error message when parsing fails
add more firendly error message here
fix a bug in stack argument explict management, stack control works now!
clean
ready for early action
new LStack seems to be buggy, this version is okay:fix
add compatiblity for ocaml 4.0
4.0 compatible