tests.

tensor/test_basic:T_scalarfromtensor.test0 which was already a known failure

This should unbreak GPU shared variables, broken after [c4a975e14f7c].

None is almost like False, except it is OK do downcast a Python float to
a scalar floatX array. Other specialized case might be added later.

Change all theanorc code blocks in docs to use the 'cfg' Pygments filter which is designed for this.

Implemented unittests which test that the contract for In is respected: we test
that aliasing the input is impossible with borrow=False.

Old theano versioning system is deprecated with DWF's latest changes. Versioning
is now handled through setup.py and mercurial hooks.