Building in 32-bit mode was only to reduce binary size on 64-bit machines
and is otherwise not needed.  Having it forced to 32-bit meant an
unnecessary dependency on 32-bit libraries that is now removed.

Same code repeated for each send*() and recv*() function.

It can happen that a socket gets closed while the pbuf is not completely
drained by the application.  It can also happen that a new pbuf comes in
via the recv callback, and then a "peer closed" event comes via the same
callback (pbuf=NULL) before the previous event has been handled.  In both
cases the socket is closed but there is remaining data.  This patch makes
sure such data is passed to the application.

For example, the peer may close the connection while recv is waiting for
incoming data.

If the heap is locked, or memory allocation fails, then calling a bound
method will still succeed by allocating the argument state on the stack.

The new code also allocates less stack than before if less than 4
arguments are passed.  It's also a tiny bit smaller in code size.

This was done as part of the ESA project.

tools/pydfu.py is now the recommended way of deploying a DFU file.  Old
behaviour of dfu-util can be obtained by passing USE_PYDFU=0 when invoking
make.

The main README.md file has been updated to reflect this change.

Now, all output has newlines converted to \n, regardless of port or
platform.

Also explicitly name the py/*.o files in the linker file, to enable easy
testing of putting certain ones in iRAM.

None of the other ports do, since introduction of mp_state_ctx_t. In
the case of current esp8266 port, heap is inside BSS, so scanning it
picked up a lot of dead pointers.

To make it easier to spot differences.

Useful for embedded targets with fixed stack layout.

NameError may either include offending name or not. Unfortunately, this
change makes test float-dependent. And using integer division leads to
different error message than CPython.