This follows source code/header file organization similar to few other
objects, and intended to be used only is special cases, where efficiency/
simplicity matters.
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/.