GC triggering performance optimizations

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

Change-Id: I454b1985a3225d7dbdea9c5d4e6f0c9f5e24352e
Merge remote-tracking branch 'github/jb43-r2.2' into HEAD

Signed-off-by: Evan Anderson <evan1124@gmail.com>

Conflicts:
	vm/alloc/HeapSource.cpp