Get rid of some unnecessary commented out code (issue #6849)

There is a lot of false positives (see [attached logs](http://code.google.com/p/sympy/issues/detail?id=3750#c1)), so I don't think that we should automate such cleanup.

fixes #6849
The example would be that it'd be nice if the fortran code printer printed code that executed floor and ceil. These comments could be there as an indication that they need to be implemented, just as you could add an xfail test to indicate that something should be implemented, or should work.