add legacy overlay support

Change-Id: I64041e9199ad01bafb3112ef2059fa503692baa3
MemoryHeapBase: ifdef for gingerbread/froyo compatibility

This change is required to use overlay based proprietary camera libs
coming from gingerbread and froyo builds.

This change also requires a global cflag named BINDER_COMPAT
because a lot of modules use the MemoryHeap includes

Add this in your BoardConfig.mk :
COMMON_GLOBAL_CFLAGS += -DBINDER_COMPAT

Backported from /#/c/13317/

Change-Id: I919a2a89d5efa0eab5ef286979fcd823b62a363c