Make Theano work under pypy (WIP)

On windows, check for intel OpenMP if gnu failed for mkl

Fix for mixed-dtype input in dnn_conv

* Fix bug of incorrect seq slice in scan with one step.

Skip test_sync_update in DEBUG_MODE because it is incompatible

The library .so file is named pypy3-c rather than pypy-c.

CPython extensions built for PyPy should be named used a special suffix
which includes the variant of Python e.g. .pypy-41.so. These can be
loaded at runtime (import module) without doing anything special and
will not be confused with regular Python CPython modules.

This call does not exist in PyPy (as it presumably doesn't refcount).

This type is unavailable in PyPy (and also unlikely to be exposed). This
just removes a type-check.

Broken link in doc to amdlibm

Fix scan MissingInputError cause by hidden var used in condition.

Doc magma

Don't ask for MKL_THREADING_LAYER=GNU if NumPy is fixed

Follow API changes in cudnn 7.1 for RNN params

Also default to clang for FreeBSD.

Try cygwin fix

Fix scan names of variables.

Support more recent flake8 version

After looking at older documentation of flake8, I think all flake8 3.* version should work: http://flake8.pycqa.org/en/3.0.0/user/python-api.html. So removing the version check completly.