Pull request gevent check

Sometimes gevent has been loaded as module but monkey patch has not been performed. (f.e: Pymongo is doing it)

With the patch I propose to check if system thread module has been "monkey patched" with gevent and then do  the right import of Queue.

Also I have added a parameter on **testall.py** to check the testsuite with gevent enabled/disabled.

Time elapsed doing the **test suite** has been improved a lot (at my desktop from 30 to 10 seconds)