[Cython] Standard include path

[Dag Sverre Seljebotn]

Two issues that may or may not overlap:

My test case has a call to malloc (tips to get around this are welcome
but I'd still like to have a look at include paths). So I'm cimporting
stdlib, meaning I have to export INCLUDE=Includes prior to running tests
(which I'd like to avoid as apparently no other tests relies on this?)

There are two ways of going about this:
- Have runtests.py always include the Includes dir
- Have Cython itself always include the Includes dir (i.e. always
../../Includes relative to Cython/Compiler/Main.py).

I prefer the latter one; thoughts? I suppose this might also mean 
installing Includes "somewhere" on setup.py (or is that already done?)

Also there's another import issue: For more sophisticated transforms,
I've (or Robert, can't remember) come up with a __cython__ namespace
which basically contains "any symbol the compiler might like to use".
For instance:

TreeFragment(u"__cython__.PyObject_GetBuffer(<__cython__.PyObject*>TMP,
&BUFINFO, 0)")

Eventually all the __Pyx-utils might be declared in this one too (though
I'm certainly not going to do it for the sake of it). Then the idea is
that __cython__ is *always* cimported (and available to the user as well).

Any strong feelings against simply making this a __cython__.pxd in the
aforementioned standard include path? Note the consequences: The
compiler will be hard-wired to work with a certain pxd file. The
alternative is to create a cython-scope similar to builtin-scope
programatically (or stick everything that is needed in symtab.py directly).


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Dag Sverre