More EH document comments

[Jason Merrill]

Sorry this is so terse...

8.3.3: setups -> sets up, notaltered -> not altered
9.2: Some of this seems obsolete, since we decided not to have an 
allocating entry point (C-6).

How do we know to call terminate() if there's no handler (rather than
some other language's semantics)?  Something in the personality of the
thrown object?

11.6: Why would we need to pass in the unexpected_handler?  Can't the runtime
get it from the exception header?  ...but what happens if there is no 
current exception?

11.11: We decided that we can catch foreign exceptions.
  "alternate return code"?  Do you mean "landing pad"?

11.12.1: 13.7 says we return the adjusted object pointer, but the sample
  implementation returns void.

11.12.2: The sample implementation won't work; we can finish exceptions 
   other than in strict LIFO order, in cases involving rethrow.
  6.1 doesn't pass the 'thrown' argument (and is the only relevant code
   sample).  Didn't you say it wasn't necessary?

Jason