Issue #783: python3 compatible - remove relative imports.

Lazy config default value

Fix a test when g++ is not available.

Add triangle/nonzero functions

We want to have it evaluated only if the config value get used. Otherwise, this will trigger compilation at import time for a following commit.

We call it only if the user didn't provide a value.

This is one of the trickier relative to absolute convertions.  Some
of the initialization code had to be moved from tensor subpackage to
the main theano __init__.py in order to work around a circular dependency.

Update comment after code review.

Fix test and update NEWS.txt

We explicitly use and -inf in the graph, so DebugMode shouldn't complain about this.

The problem was caused by the name conflict between the scan submodule and the scan function.

This reverts commit 7fa448b8.

make filter for CudaNdarray check for stride == 0 for dim == 1.

Conflicts:
	theano/compile/function.py
	theano/compile/pfunc.py
	theano/gof/fg.py
	theano/gof/type.py