Provide python logging compatibility in eventlet.wsgi

Provide a compatibility layer in eventlet.wsgi that allows you
to hand a python logger as the log parameter instead of a
filehandle. This is done via an object wrapper so the logging
methods will only be used if the contents of the log parameter
look like a log, otherwise the previous behavior of just writing
to the logger is done instead.

This also will emulate the log(msg, *args) behavior on the
filehandle method so more advanced logging can be used.