android/base/Log.h: Fix DPLOG() implementation.

This patch fixes the implementation of android/base/Log.h to properly
compile DPLOG() statement, and set ENABLE_DLOG explicitly during the
build.

Change-Id: Id2c64ffdfe33946c6a08f66a90dc7975ace006a2
Merge "android/base/Log.h: Fix DPLOG() implementation."