Do not repeat a variable in a function's inputs

Simplified code for In.borrow and Param.borrow

That's the reason why DebugMode was complaining.

Broadcast input of sparse_from_dense so ndim=2

Fix dtype of input value in test_diag

Since csc_matrix's default dtype is floatX, the numpy value needs
to have a compatible dtype.

Do not constant-fold Alloc if it is the output

Since mutable=True is incompatible with borrow=False, it is better to
raise an exception to make sure it's being noticed.

make_node used to crash, now it works.
A test detects the problem.

This makes things easier for shape inference and gradient operations.
Also fix broadcasting pattern of the gradient.

This commit simplifies the code so that In.borrow and Param.borrow can
only be True or False (not None). It also makes the corresponding code
for these two objects more similar.

There should be no functional change, it just makes the code easier to
understand.

Finished DOC/TEST/REVIEW sparse Diag Op

Fix test_diag_grad to work with verify_grad

Also fix an optimization bug in that case.

Fix perform of structureddot_grad with dense grad

Include "canonicalize" in tests for shape opt.

Fix comparison of "borrow" flag.

This was causing lots of warnings to print in the buildbot.
The error was introduced during a seemingly innocent PEP8 fix.

Update code for mean's dtype after code review

Miscellaneous documentation updates

Remove duplicated code.

This seems like the result of a bad merge.