Updated teensy to build.

Refactored some stmhal files which are shared with teensy.
Added hexfile target
Add timer_deinit and call it just before doing a soft-restart

This fixes #733.
Merge branch 'teensy-new' of github.com:dhylands/micropython into dhylands-teensy-new

Conflicts:
	stmhal/pin_named_pins.c
	stmhal/readline.c

Renamed HAL_H to MICROPY_HAL_H.  Made stmhal/mphal.h which intends to
define the generic Micro Python HAL, which in stmhal sits above the ST
HAL.
Merge branch 'dhylands-teensy-new'
Merge pull request #709 from windelbouwman/master

Added hexfile target
Merge branch 'add-timer-deinit' of github.com:dhylands/micropython into dhylands-add-timer-deinit
stmhal: Some reordering of code/functions.
Merge branch 'dhylands-add-timer-deinit'
Add support for storing args during an exception raised by an irq.

The user code should call pyb.alloc_emergency_exception_buf(size)
where size is the size of the buffer used to print the argument
passed to the exception.

With the test code from #732, the following error is now printed:
```python
>>> import heartbeat_irq
Uncaught exception in Timer(4) interrupt handler
Traceback (most recent call last):
  File "0://heartbeat_irq.py", line 14, in heartbeat_cb
NameError: name 'led' is not defined
```