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/.
It's really a UART because there is no external clock line (and hence no
synchronous ability, at least in the implementation of this module).
USART should be reserved for a module that has "S"ynchronous capabilities.
Also, UART is shorter and easier to type :)