This is how it should be, so one knows exactly where the includes are
coming from.

Now all ports can use pybstdio.c to provide sys.stdin/stdout/stderr, so
long as they implement mp_hal_stdin_* and mp_hal_stdout_* functions.

This change helps making the cc3200 port API a bit closer to stmhal.
The ramaining differences are due to the specific hardware details
of each chip. One feature that has been deliberately disabled is the
possibility to add custom names and custom pin mappings. Those
features are nice and convenient, but in this port, code size is a
major concern.

The port currently implements support for GPIO, RTC, ExtInt and the WiFi
subsystem. A small file system is available in the serial flash. A
bootloader which makes OTA updates possible, is also part of this initial
implementation.