remove dependency on structmember.h

[dalcinl]

We could get rid of structmember.h by using the a code transform to manage cdef public/readonly members via properties.

Pros:

1) structmember.h has no namespace protection using a Py_ prefix for the many 'T_XXX' definitions. This can conflict with user code (BTW, and this issue was reported in cython-users ML).

2) when using PyMemberDef? tables from structmember.h, C <-> Python conversions are outside Cython's control of to_py/from_py converters. Using a transform+property mechanism is more consistent, and actually extend (for free, with no special casing at all) the types that can be made cdef public/readonly members (e.g. complex numbers, C struct's)

Cons:

1) Generated code is less readable and larger

[dalcinl]

Fixed:  http://hg.cython.org/cython-devel/rev/1a2e04bc1395