A new patch is attached.  Please review.

I decided to remove the fix for recursive __cause__.  Currently, `raise e from e` doesn't cause any problem, and if we fix the interpreter to raise an RuntimeError in such cases it will be a backwards incompatible change.  I don't see any point in introducing such a change in a bugfix Python release.  We can open a separate issue for 3.6 though.

Fixing __context__ in 3.5.2 is way more important, since the interpreter can actually infinitely loop itself in some places.  And since there is no syntax for setting __context__ manually (as opposed to __cause__ via raise .. from), I suspect that there will be much less people affected by this fix.