Add various backports of Python 2.6 builtins: next(), any(), all(), bin()

This module contains four backports of Python 2.6 methods:
next() from Ross Brattain
any() from http://stackoverflow.com/questions/3785433/python-backports-for-some-methods
all() from http://stackoverflow.com/questions/3785433/python-backports-for-some-methods
bin() from http://code.activestate.com/recipes/576847/

These backports should be conditionally imported upon exception so they
do not shadow the builtin function on newer Pythons.

Example:

try:
    any([True])
except NameError:
    from autotest.client.shared.backports import any

Justification:

Using backports for builtin functions allows for forward-compatibility and
better performance on newer python versions.

bin() is used heavily when decoding hardware register bits.
any() and all() are useful for generators and list comprehensions
next() is useful because of the default argument, and it is consistent with
Python 3 usage.

Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>
backports_unittest: unit tests for backported any(), all(), bin(), next()

Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>