py: Enable struct/binary-helper to parse q and Q sized ints.

Addresses issue #848.
Add LIS3DSH accelometer support to staccel.py
Merge pull request #852 from techno/staccel_LIS3DSH

Add LIS3DSH accelometer support to staccel.py
py and libm: Add asinf,acosf; print higher precision for float.

Also use less stack space when printing single precision float.

Addition of asinf and acosf addresses issue #851.
Merge branch 'master' of github.com:micropython/micropython