The user code should call micropython.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, and a call to
micropython.alloc_emergenncy_exception_buf(100) 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
```

Add GNUmakefile to the .gitignore file.

Addresses issue #765.

Allow DFU_UTIL to be overridden from the environment.

Enable 16-bit memory addresses for i2c.mem_read and i2c_mem_write

Deal with reading a buffer less than what was allocated.

to maintain compatibility with existing code.

With this fix, file_long_read now passes.

Currently broken for unicode input streams.

Recent changes to builtin print meant that print was printing to the
mp_sys_stdout_obj, which was sending data raw to the USB CDC device.
The data should be cooked so that \n turns into \r\n.

Fixes printing bugs introduced by
cb66f41e.

And not system printf(), like it was before. For this, move pfenv_printf()
from stmhal port to py/.

Add fsync for windows, i.e. _commit. See dce8876d

py: Add stream reading of n unicode chars; unicode support by default.

With unicode enabled, this patch allows reading a fixed number of
characters from text-mode streams; eg file.read(5) will read 5 unicode
chars, which can made of more than 5 bytes.

For an ASCII stream (ie no chars > 127) it only needs to do 1 read.  If
there are lots of non-ASCII chars in a stream, then it needs multiple
reads of the underlying object.

Adds a new test for this case.  Enables unicode support by default on
unix and stmhal ports.

Addresses issue #753.

Add teensy core files and use same toolchain as stmhal

Fix teensy to build on latest tree.

Put #include of mpconfig.h before misc.h
Replace uses of ARRAY_SIZE with MP_ARRAY_SIZE

This method apparently should be part of stream interface.

This script uses expected test results as generated by run-tests --write-exp,
and requires only standard unix shell funtionality (no bash). It is useful
to run testsuite on embedded systems, where there's no CPython and Bash.

emitnative in particular requires nlr_* to be real functions, so doesn't
compile with MICROPY_NLR_SETJMP=1.

Mostly to run testsuite on targets which doesn't have CPython.