It defines types used by all other headers.

Fixes #691.

Refactored some stmhal files which are shared with teensy.

TODO: Get rid of this compatibility define and rely on standard module.

Blanket wide to all .c and .h files.  Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.

Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.

Make include dependencies neater, and adheres to the coding convention
that headers should not include headers.

Addresses issues #272 and #273.

* Issue #232

To partly address Issue #220.