GC triggering performance optimizations

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

Change-Id: I1080ba60ae64d546c0f35925bc7c931b89c7600b
dalvik/vm: Dalvik startup with a low memory footprint

Initialize concurrentStartBytes and createMspace using HEAP_MIN_FREE.
This helps save Android framework memory after boot.

This is for low memory targets only(~512MB RAM & hdpi resolution)
Also, set TARGET_ARCH_LOWMEM in the BoardConfig.mk file of a device
for this patch to take effect.

Change-Id: Ib164c5eaf3236fe2de2697e84de4ee85f8997e94