Compilation failure with Python 3.2

Boost 1.65.1 fails to compile on Debian Wheezy with Python 3.2:

```
libs/python/src/numpy/ndarray.cpp: In function 'boost::python::numpy::ndarray::bitflag boost::python::numpy::detail::numpy_to_bitflag(int)':
libs/python/src/numpy/ndarray.cpp:25:11: error: 'NPY_ARRAY_C_CONTIGUOUS' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:26:11: error: 'NPY_ARRAY_F_CONTIGUOUS' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:27:11: error: 'NPY_ARRAY_ALIGNED' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:28:11: error: 'NPY_ARRAY_WRITEABLE' was not declared in this scope
libs/python/src/numpy/ndarray.cpp: In function 'int boost::python::numpy::detail::bitflag_to_numpy(boost::python::numpy::ndarray::bitflag)':
libs/python/src/numpy/ndarray.cpp:35:39: error: 'NPY_ARRAY_C_CONTIGUOUS' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:36:39: error: 'NPY_ARRAY_F_CONTIGUOUS' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:37:34: error: 'NPY_ARRAY_ALIGNED' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:38:36: error: 'NPY_ARRAY_WRITEABLE' was not declared in this scope
libs/python/src/numpy/ndarray.cpp: In function 'boost::python::numpy::ndarray boost::python::numpy::detail::from_data_impl(void*, const boost::python::numpy::dtype&, const std::vector&, const std::vector&, const boos
libs/python/src/numpy/ndarray.cpp:122:27: error: 'NPY_ARRAY_WRITEABLE' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:123:59: error: 'NPY_ARRAY_C_CONTIGUOUS' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:124:59: error: 'NPY_ARRAY_F_CONTIGUOUS' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:125:47: error: 'NPY_ARRAY_ALIGNED' was not declared in this scope
libs/python/src/numpy/ndarray.cpp: In function 'boost::python::numpy::ndarray boost::python::numpy::array(const boost::python::api::object&)':
libs/python/src/numpy/ndarray.cpp:246:45: error: 'NPY_ARRAY_ENSUREARRAY' was not declared in this scope
libs/python/src/numpy/ndarray.cpp: In function 'boost::python::numpy::ndarray boost::python::numpy::array(const boost::python::api::object&, const boost::python::numpy::dtype&)':
libs/python/src/numpy/ndarray.cpp:252:65: error: 'NPY_ARRAY_ENSUREARRAY' was not declared in this scope
libs/python/src/numpy/ndarray.cpp:253:1: warning: control reaches end of non-void function [-Wreturn-type]
libs/python/src/numpy/ndarray.cpp: In function 'boost::python::numpy::ndarray boost::python::numpy::array(const boost::python::api::object&)':
libs/python/src/numpy/ndarray.cpp:247:1: warning: control reaches end of non-void function [-Wreturn-type]
```