Removed shared / shared_constructor / pfunc from compile.sandbox, please use theano.shared / theano.function instead

Added option config.on_opt_error to decide between a warning vs an exception when a crash occurs in an optimization

Added the option to hide warnings about cuda not being found by setting config.cuda.root to an empty string

debug mode such to ignore memory buffer provided to the linker to store its
outputs in them.

mq is nice, but sometimes it screws up where the patch gets applied...

later harder ( we would need to check if two scan have the same
mode_instance class or the same instance when we decide to merge??)

So if tall c code is already compiled, we don't take it!