change: fork function return a nil on failure.
change: build process has been changed.
add: helper macro lstate_bool2tbl has been added.
add: waitpid function has been added.
add: test/sleep_try.lua has been added.
add: test/fork_try.lua has been added.
fix: should add a result pid to status table for usability reasons.
add: test/waitpid_try.lua has been added.
remove: unused files has been removed.