Treating it as signed lead to buffer overflow for ports >= 32768.

This usually allows to get just a single address entry.

This requires root access. And on recent Linux kernels, with
CONFIG_STRICT_DEVMEM option enabled, only address ranges listed in
/proc/iomem can be accessed. The above compiled-time option can be
however overriden with boot-time option "iomem=relaxed".

This also removed separate read/write paths - there unlikely would
be a case when they're different.

Update pydfu.py to match with the version from openmv.

I just updated the openmv version to work with both of the
PyUSB 1.0.0.b1 and 1.0.0.b2

See: https://github.com/walac/pyusb/blob/master/ReleaseNotes.rst

I checked the entire codebase, and every place that vstr_init_len
was called, there was a call to mp_obj_new_str_from_vstr after it.

mp_obj_new_str_from_vstr always tries to reallocate a new buffer
1 byte larger than the original to store the terminating null
character.

In many cases, if we allocated the initial buffer to be 1 byte
longer, we can prevent this extra allocation, and just reuse
the originally allocated buffer.

Asking to read 256 bytes and only getting 100 will still cause
the extra allocation, but if you ask to read 256 and get 256
then the extra allocation will be optimized away.

Yes - the reallocation is optimized in the heap to try and reuse
the buffer if it can, but it takes quite a few cycles to figure
this out.

Note by Damien: vstr_init_len should now be considered as a
string-init convenience function and used only when creating
null-terminated objects.

Previous to this patch, if "abcd" and "ab" were possible completions
to tab-completing "a", then tab would expand to "abcd" straight away
if this identifier appeared first in the dict.

Drops Thumb2 arch size by 24 bytes.

Stream methods were added to normal sockets as in the unix port.

WLAN needs time info when validating certificates.