Since all currently supported boards use pin A9 for this function, the
value of the macro MICROPY_HW_USB_VBUS_DETECT_PIN is not actually used,
just the fact that it is defined.
Addresses issue #1048.
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/.