Add dalvik.vm.gctype to enable switching between different GCs.
Add dalvik.vm.gctype to enable switching between different GCs.

The option passes the specified GC type into the Xgc runtime
option.

Currently the three different supported GC types are MS, CMS, SS
which represent mark-sweep, concurrent mark-sweep, mark-sweep +
semi-space hybrid.

Change-Id: I6ad95c8d12c0d1158f7c861ff0c3180761619172

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base