This makes exception traceback info self contained (ie doesn't rely on
list object, which was a bit of a hack), reduces code size, and reduces
RAM footprint of exception by eliminating the list object.

Addresses part of issue #1126.

Slightly smaller code, and does not need to use C stack to save
temporaries.

Before, both mutexes and semaphores were used. Using only the latter
and with a bit of cleanup to remove some code bloat, we save ~600
bytes of code.

This helps saving ~300 bytes. Thanks to dpgeorge.

The safe boot pin, when pulled high during reset rolls back the
firmware to the "factory" image and skips execution of 'boot.py'
and 'main.py'. This is useful to recover from a crash condition.
The system led is used mostly to signal errors.

Addresses issue #1132.

Also improve pybsd, and make it save it's pin configuration.
This is a necessary step towards supporting the CC3200 low
power deep sleep (LPDS) mode.

Reduces stmhal by about 300 bytes ROM.

Also, reword purpose to avoid impression that uPy supports just one
microcontroller.

This function is only used when DEBUG_PRINTERS and USE_RULE_NAME are
enabled.

Still too shy to implement UnicodeEncodeError which was really needed for
micropython-lib case.

These definitions help on making modwlan.c usable by other ports
with the CC3100.

Also change other methods' names to make them consistent.

In particular, make sure that the globals are all initialized
before enabling the interrupt, and also make sure that the timer
interrupt has been initialied before enabling the NVIC.

Those trace messages have never proven to be useful and they make
the code 9K bigger.

Use the simplelink wrappers instead. This is one step further
towards having a single module for the cc3200 and the cc3100.

The implementation of these functions is very large (order 4k) and they
are rarely used, so we don't enable them by default.

They are however enabled in stmhal and unix, since we have the room.

Also includes documentation about minimum baudrate.

Addresses issue #1090.