speed up debugmode. Don't use intermediate call.

Also, make less call to may_share_memory.
speed up misc.may_share_memory()
Don't precompute stuff if it isn't used.
speed up debugmode, less fct call.
fix crash just introduced
a few other small crash fix just introduced
More check and move to GPU the symbolic input if needed.
Some extra comment in c code to help find our way while reading it.
Add extra printout in the buildbot.
Document Type.may_share_memory and implement it in Scalar.
Add 780 timming.
Merge pull request #1955 from nouiz/debugmode

Speed up Debugmode
Opt that remove useless Tile Op.
Add a better string reprensentation of Tile.
Merge pull request #1965 from nouiz/tile

Opt that remove useless tile