TypeList.may_share_memory more resilent to different input type.

This was detected by a crash in DebugMode in the Theano buildbot as
another change made Type.may_share_memory obligatory in DebugMode. As
this discovered a bug, I'll keep this mandatory.

This fix a test in the buildbot.

Don't change the defaul log level during import. Otherwise, the user can...

Argparse is in Python 2.7. This file was added for compatibility with
older python.

We remove one of its user(nose_pr.py) that we don't use.

As we support python 2.6, I raise a good error message in the only
file that use it. As it is available in pypi, I think it is fine we
don't provide it for python 2.6, as this file isn't very important.

Don't change the defaul log level during import. Otherwise, the user can't get the log level he want during theano import.

fix gh-2130

Fix memory leak in scan related to the input and output storage of the inner function.

Fix blocksparse optimization that could give bad results in some cases

[ENH] Add SliceConstant, better stack trace, fast_compile_gpu

Also add patch for numpy API fixes to help people playing with scan_perform.pyx

This is because if we exclude the 'gpu' tag, we don't want those opt to also be enabled.

Remove internal Theano stack level from variable creating. This make them more readable to the user.

The added test currently fail.

[MRG, ENH]Some crash/warning fix and skip some tests when g++ isn't available.

fix gh-2138

Fix destructor handling in CDataType for python 3/Capsules.