Implements max pooling rop which works with both stride and padding. Both
variables can be symbolic. Also defined Rop for average and sum pooling. For
average or sum, Rop is simply op called on eval_points.

Make join work inplace

Fix opt crash

Update NEWS_DEV.txt and .mailmap

Python2 3

Skip another test when cxx isn't available.

Still merge identical Asserts while Assert merging is disabled

Try to get_scalar_constant_value for Assert nodes

Remove isnan from the graph for discrete dtype.

Although the fancy merging of conditions is disabled, identical Asserts
can still be combined. See #3344.

close file with context manager

Conda fixes

GPU gemv->dot speedup for new backend

Jenkins release scripts

Fix tests when no compiler.

Since each of Anaconda/Miniconda/conda-forge change sys.version to
contain different things, and some users may install MKL outside
of conda, always try the import and then, if using conda, give some
useful information on how to install MKL (by installing `mkl-service`
not `mkl`).

Many Windows users avoid the command-line and are unfamiliar with env. vars.
They can elect to use Anaconda/Miniconda Python as their system Python and
in that case would not be able to take advantage of g++ or mkl.

This commit works around these issues by adding the appropriate values to
os.environ['PATH'] if they are not already on PATH.