Saves 320 bytes on x86.

unix-cpy was originally written to get semantic equivalent with CPython
without writing functional tests.  When writing the initial
implementation of uPy it was a long way between lexer and functional
tests, so the half-way test was to make sure that the bytecode was
correct.  The idea was that if the uPy bytecode matched CPython 1-1 then
uPy would be proper Python if the bytecodes acted correctly.  And having
matching bytecode meant that it was less likely to miss some deep
subtlety in the Python semantics that would require an architectural
change later on.

But that is all history and it no longer makes sense to retain the
ability to output CPython bytecode, because:

1. It outputs CPython 3.3 compatible bytecode.  CPython's bytecode
changes from version to version, and seems to have changed quite a bit
in 3.5.  There's no point in changing the bytecode output to match
CPython anymore.

2. uPy and CPy do different optimisations to the bytecode which makes it
harder to match.

3. The bytecode tests are not run.  They were never part of Travis and
are not run locally anymore.

4. The EMIT_CPYTHON option needs a lot of extra source code which adds
heaps of noise, especially in compile.c.

5. Now that there is an extensive test suite (which tests functionality)
there is no need to match the bytecode.  Some very subtle behaviour is
tested with the test suite and passing these tests is a much better
way to stay Python-language compliant, rather than trying to match
CPy bytecode.

The nss param in the pyboard has a different meaning that doesn't
apply to the WiPy.

Rename "wakes" param to "wake_from" and make "value" an object
instead of an integer.

- add SEEK_XXX definitions, this fixes missing definition in py/stream.c
- move R_OK from realpath.c and add W_OK/F_OK defintions
- move STDXXX_FILENO definitions from mpconfigport for consistency

r7 may be needed to set up code state, so it must be loaded before the
set-up function is called.

Addresses issue #1420.

On the first boot don't add the MAC address, this is to speed up
factory testing.

This bug was introduced when renaming '/sflash' to '/flash'.

The first safe boot level executes the latest firmware but skips
'main.py' and 'boot.py'.

Key is always entered as a string, but if security is WEP, the key
is converted automatically to hex before connecting or configuring
the device as an AP.

Changes are based on this post:
https://github.com/micropython/micropython/issues/876#issuecomment-115255551

The constructor can optionally take the same params of iwconfig in
order to configure WiFi when creating the object. Params are
keyworkd only. The WiPy accepts:

- mode (int -> WLAN.AP or WLAN.STA)
- ssdi (string)
- security (int -> WLAN.OPEN, WLAN.WEP, WLAN.WPA, WLAN.WPA2)
- key (string)
- channel (int (1-11))
- antenna (int -> WLAN.INTERNAL, WLAN.EXTERNAL)