Remove homebrewed SWIG code if possible

[Jan Blechta]

In dolfin/swig/typemaps/primitives.i there are two comments

//-----------------------------------------------------------------------------
// A home brewed type check for checking integers
// Needed due to problems with PyInt_Check from python 2.6 and NumPy
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
// Home brewed versions of the SWIG provided SWIG_AsVal(Type). These are needed
// as long as we need the PyInteger_Check. Whenever Python 2.6 is not supported
// we can scrap them.
//-----------------------------------------------------------------------------

about homebrewed wrappers needed in Python 2.6. As 2.7 is now required their removal could simplify the interface code, reduce generated wrapper code and be more robust for 64-bit PetscInt which is tricky to handle, see for instance 8e9ccab, #366, #377.

[Anders Logg (Chalmers)]

Removing milestone: 1.7 (automated comment)

[Prof Garth Wells]

Will be resolved by dropping SWIG (#896).