MAINT: merge scalarmathmodule into umath module

There is no good reason it needs to be its own module.
Also removes the undocumented pymath alter/restore functions.
DOC note the effect of #1866 in byteorder discussion
BUG: fix header using symbols not available in py3

Inside numpy we handle this via the py3kcompat header which is not
really public api. So for our public headers we need some explicit
checks.
Merge pull request #5257 from juliantaylor/py3-header-fix

BUG: fix header using symbols not available in py3
MAINT: use scikit-image wheels collection

An attempt to address Cython build failures.
Mention transport argsort for inverting the transposition
ENH: added std::complex support to numpy.i

numpy.i now includes ready-made typemaps for std::complex<float>
and std::complex<double> .  Tests were added to testArray using
a newly defined ArrayZ class.
MAINT: add --no-cython-compile flag for Cython

Add flag to prevent Cython compiling itself.  This speeds Cython
installation and doesn't much slow down pyx file building.

From suggestion by Nathaniel.
Merge pull request #5265 from matthew-brett/rackspace-cython

MAINT: use scikit-image wheels collection
ENH: add `multi_dot`: dot with multiple arguments.

`np.linalg.multi_dot` computes the dot product of two or more arrays in
a single function call, while automatically selecting the fastest evaluation
order.

The algorithm for selecting the fastest evaluation order uses dynamic
programming and closely follows:

    Cormen, "Introduction to Algorithms", Chapter 15.2, p. 370-378
DEP: Replaced arr->nd with PyArray_NDIM in fortranobject.c
DEP: replaced arr->nd with PyArray_NDIM in C code generation scripts
DEP: replaced arr->data with PyArray_DATA
DEP: replaced arr->dimensions with PyArray_DIMS(arr) or PyArray_DIM(arr,i)
DEP: Replaced arr->descr, arr->flags and arr->base with the PyArray_* functions
DEP: Using PyArray_SIZE and PyArray_TYPE instead of PyArray_DESCR()->elsize etc
DEP: Using the internal PyArrayObject_fields API for the swap_arrays and dump_attrs functions
DEP: Replaced NPY_[F,C]ARRAY with NPY_ARRAY_[F,C]ARRAY
DEP: Corrected some type errors that appear when enabling NPY_NO_DEPRECATED_API
DEP: Replace NPY_CONTIGUOUS with NPY_ARRAY_C_CONTIGUOUS