Fix optimization warning due as we didn't returned the right dtype for empty matrix in ExtractDiag.
fix error in the doc reported by abalkin in gh-1098
Minor code clean-up
Removed useless return in __init__

This can just cause confusion.
Merge pull request #1099 from nouiz/fix_crash_extract_diag

Fix optimization warning due as we didn't returned the right dtype for e...
Corrected a few typos in scan documentation.
Merge pull request #1101 from abalkin/doc-fixes

Corrected a few typos in scan documentation.
Fixed a source of non-determinism
PEP8 fixes
pep8
backport to python 2.4
fix test when floatX=float32.
pep8
Turned errors into warnings for merge
Merge pull request #1100 from delallea/determinism

Fix for a source of non-determinism
fix hashlib import issue (thanks Olivier)
Merge pull request #1103 from goodfeli/master

Fix import issue Olivier caught after my last PR was merged
Merge pull request #1102 from nouiz/py24

Fix tests
Fixed crash in constant folding optimization
No Alloc constant folding when no clients

This is because either:
- There will never be any client and thus the node will be pruned, so
  performing constant folding would be a waste of time, or
- Someone will add clients later and will re-run the constant folding
  phase, in which case we will want to use the client-dependent logic to
  decide whether constant folding should be applied or not.