Removed excessive GC freed lines instead disable them

CM has introduced a method to disable GC freed lines by setting dalvik.vm.debug.alloc to 0. See http://review.cyanogenmod.org/#/c/45785/
Now I doubt whether this method is effective or even could make the dalvik performance worse than before.
This method checks the property of dalvik.vm.debug.alloc and convert the property value from string to integer everytime before dalvik writes debug line to logcat.
It is probably better to let dalvik to do only one operation to write debug line rather than to do two operations:
* Looking a property from a map that could contains hundred of properties
* Converting property value from string to integer
Since Heap.cpp is not a class, we cannot have a member variable that holds the dalvik.vm.debug.alloc value by reading it only once.

Remove the debug lines together with other information that are used in the debug line.

Change-Id: I164584bc3f53e5471a2e194125a867fd244a5774