[4.8] Add Andrew Hsieh's -foptimize-sincos patch

Bionic prior to Gingerbread doesn't support sincos*, but upstream GCC
enables sincos optimization for OPTION_BIONIC unconditionally since
4.6.  I'd like to propose a new flag -foptimize-sincos for NDK to
maintain backward compatibility.

1. For BIONIC: sincos optimization is disabled by default.  Apps built
for Gingerbread+ or AOSP platform build which uses the same compiler
as NDK, can add -foptimize-sincos to enhance performance.  (although
it's likely that only benchmarks may benefit)

2. Other C libs aren't affected.  sincos optimization is enabled for
GLIBC and disabled for othres, regardless of this flag.