fix the new approach using buttons :
https://github.com/mindboards/ev3dev-kernel/issues/24
fix issues.
fix issues.
Merge branch 'master' of https://github.com/cho934/ev3dev-lang.git
Merge branch 'master' of https://github.com/cho934/ev3dev-lang.git
Merge branch 'master' of https://github.com/cho934/ev3dev-lang.git
replace calloc by new/delete.
Merge pull request #5 from cho934/master

fix the new approach using buttons