pull request for hotfixes

1. Passed checks in ./script/checkpatch.pl 
2. Fixed two bugs:
     a) fix a typo, otherwise we can not pass compile under vanilla 2.6.32 kernel.
     b) make orig_stub always is a valid original function pointer or NULL, so we can invoke original function across 
        multiple hotfixes after checking simple check whether the original function pointer is NULL.