GC triggering performance optimizations

Copy the correct starting heap size at process init.
Interfaces to set GC/managed heap parameters.

 Changes to be committed:
	modified:   build/phone-xhdpi-1024-dalvik-heap.mk
	modified:   build/phone-xhdpi-2048-dalvik-heap.mk
	modified:   build/tablet-10in-xhdpi-2048-dalvik-heap.mk
	modified:   build/tablet-7in-hdpi-1024-dalvik-heap.mk