Need to change syntax for pxd function typing

[dagss]

The new inline pxd functions conflicts in syntax with the recently introduced method of having a pure Python function in the .py file and the types for the function in a corresponding pxd file. Cython 0.11 should not be released without fixing the syntax we want to support for the future so I made this a blocker.

The scheme settled on in mailing list:

> > I'm generally -1 on adding new syntax, but what I had wasn't very  
> > clear either. Would it be enough to accept a locals decorator?

I think that's a very clean compromise. You can

a) specify the signature in .pxd files as you would in .pyx files, just
without a function body.

b) write importable inline functions in .pxd files as a function with body,
just as you would in a .pyx file.

c) specify local variable types for a .py implemented function in a .pxd
file by adding a decorator to a function signature, but without providing a
function body.

So, whenever a function signature in a .pxd file has a body at all, it must
be a complete inline function.

I actually don't think that users would intuitively expect the current way
of defining local variables in .pxd files to work.

Note that this may require extending decorator support (in Parsing.py) to cdef functions. They should all probably simply be let through, and then disallowed again (except for @cython.locals) in PostParse?.

[dagss]

I think #143 could be partially fixed and made a feature request instead by at least disallowing the current way of typing local vars in pxd files, without necesarrily introducing a new way of doing it.

[dagss]

Fix attached, this can be closed when I get to push it or someone else applies it.

[dagss]

NB''' The comments above were for #200, this was for the wrong ticket. (Now where have those edit and delete buttons gone to in this Trac version -- yes, I'm still TRAC_ADMIN...hmmm...)