Because Numpy 1.8.0 will no longer supports Python versions < 2.6 we
no longer need to check for that and can also remove the code that is
specific to those earlier versions.

To make this a bit safer, the toplevel setup.py file now contains a
check of the Python version number and raises an error when run by an
unsupported version.

See https://github.com/scipy/scipy/pull/279

npy_3kcompat.h is semi-private, so this can be done.

Moves PyDataMem_NEW/FREE/RENEW to the external API.
Fixes PyDataMem_NEW/RENEW to return void* instead of char*.
Replaces PyDataMem_NEW/FREE with NpySortArray_malloc/free in sort.c.src
  (should be reverted if npysort is moved to be part of multiarraymodule).
Adds PyDataMem_SetEventHook which takes a (PyDataMem_EventHookFunc *) as an argument,
  with signature:
       void hook(void *old, void *new, size_t size).
  When not NULL, hook will be called at the end of each PyDataMem_NEW/FREE/RENEW:
   result = PyDataMem_NEW(size)        -> (*hook(NULL, result, size)
   PyDataMem_FREE(ptr)                 -> (*hook(ptr, NULL, 0)
   result = PyDataMem_RENEW(ptr, size) -> (*hook)(ptr, result, size)
Adds tests in multiarray_tests.c.src, driven by tests/test_multiarray.py.

versioned

The interp function was computing slopes for all intervals, even when there
were only a few points to be interpolated. Now it only does so when the
number of interpolation points exceeds the number of sample points.