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

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.

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.

Fixed crash with Composite support code and GPU

The problem was that when a Composite Op had a Composite subnode, having
the subnode return an empty support code would cause the parent node to
return '\n' as support code. As a result, GPU code generation would
crash due to non-empty support code.

Thanks to Fred for writing the associated test.

Make a machanism to don't have Alloc and GpuAlloc constant folded in som...

pep8 fix + added verbose exception

Small fixes

Add shape inference for sparse/basic.py Ops

A few PEP8 fixes, string formatting and cosmetic stuff.

more pep8 fixes

various other pep8 fixes so that being pep8 compliant doesn't take as
much time

Some more typo fixes & co