Minor nio cleanup.

Manually cherry-picked
Fix the exception thrown by getDeclaredFields if the class is unavailable.

http://b/issue?id=2634005

Conflicts:
	vm/reflect/Reflect.c
Move Alloc.c to Alloc.cpp
Move CardTable.c to cpp
Move Copying.c to cpp
Move vm/alloc/DdmHeap.c to cpp
Move HeapBitmap.c to cpp

and add DlMalloc.cpp but can't use it for now
Move Heap.c to cpp
Move HeapDebug.c to cpp
Move AllocTracker.c to cpp
Move some C files to cpp
Move some C files to cpp
Move some C files to cpp
Move Jni.c to Jni.cpp
Move JarFile.c to cpp
Move some C files to cpp
Move some C files to cpp
Move some C files to cpp