Clang: Silence warnings

With GCC >=4.7 Clang generates a lot of noise with various compiler flags,
and can even break the builds when using Flags like Graphite.  This can be
reproduced by doing the following:

Setting TARGET_EXTRA_CFLAGS with Graphite flags such as these
TARGET_EXTRA_CFLAGS +=  -fgraphite-identity \
                        -floop-block \
                        -floop-strip-mine \
                        -ftree-loop-distribution \
                        -ftree-loop-linear

Causes the following errors to occure and the builds to fail:

clang: error: argument unused during compilation: '-fgraphite-identity'
                                                  '-floop-block'
                                                  '-floop-strip-mine'
                                                  '-ftree-loop-distribution'
                                                  '-ftree-loop-linear'

Silence the errors by passing the -Qunused-arguments for CFLAGS

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
C++11: turn off error warning for only the error we want to turn off

previously was setting -Wno-error to get arround C++11 narrowing violations

Change-Id: I620b1d524bce4642f3f0b4af446e00394177e42b

Conflicts:
	Android.mk
CLANG: Workaround for violations on unsupported command -mtune=cortex-a15

Clang doesn't support -mtune=cortex-a15 and newer ones will error out if this
is assigned.

Change-Id: Idf3b8850314717f99d0cdda65490f5af5c336fc8

Conflicts:
	Android.mk