tools: Add script to generate a ChangeLog file.

We don't have an explicit ChangeLog file, but don't really need one
because we use a good version control system.  This script is useful if
you need a pretty-printed ChangeLog for some reason.
py: Partially fix float to int conversion.

This fixes conversion when float type has more mantissa bits than small int,
and float value has small exponent. This is for example the case of 32-bit
platform using doubles, and converting value of time.time(). Conversion of
floats with larg exponnet is still not handled correctly.
run-tests-exp.sh: Typo fix in comment.
py/asm*.c: Typo fixes in comments.
emitnative: Incomplete implementation delete_fast operation.
py: Basic implementation of hotpath recording.
modffi: Support open own executable using open(None).
modffi: Support return values of mp_obj_t type.
unix: Support readline history saving to file, improves interactive usage.
modffi: Add .addr() method to just get symbol address.
binary: Rework array accessors. They work with native, not stdint types.
modffi: Add toplevel func() function to create a function by pointer.