New Theano flag on_unused_input that default the default value.

revert 187603d6 sa this break tests and cause problem with the grad in conjunction with the default value or on_ununsed_input.

in {zeros,ones}_like, don't insert fill for scalar.

Fix tests error when scipy is not there

Improved testing of preallocated outputs in DebugMode

Fix a Scan test. It is normal both scan got merged.

This  make  the  graph  before  compilation  and  when  compiled  with
FAST_COMPILE   more    readable.   This   was    optimized   away   to
local_fill_to_alloc, but if  we enable it in fast_compile,  it also do
more optimisation that make the  graph not readable without enabling even
more optimization in fast_compile.s

This reflects the fact that the C linker is not necessarily the problem,
and that this exception is also raised when different calls to the same
thunk (for instance, with different preallocated outputs) give different
results.

Also, do not return a preallocated map it if is empty,
and fill "previous" storage with default value.

Otherwise, we have to allocate 2**ndims times the amount of memory,
and 2**4 seems enough.

Also, strides 1 and -1 will not be tested independently on the
dimensions above 4, their strides will always be all 1 or all -1.

The += syntax is not implemented for dims > 5.
Also actually use a tensor of wrong size in "wrong_size" mode.

If an input is viewed, and the corresponding output is destroyed,
then it destroys the input.
There would be ways to be more precise, but at least this is correct.

Fix test

Fix scan debugmode

Fix scan debugmode

destroy_map is not always defined for a scan op.