This reverts commit 4900109c.
This is trying to parallelise the appveyor build again after allowing the setup.py script to be imported on a multiprocessing "spawn".

This reverts commit 52635828.

multiprocessing requires some additional setup on Windows, which I don't currently want to implement in setup.py.

* Rewrite the test code generation for the unicode normalisation test, making sure that we always write UTF-8 source files.

* Fix failures to print the compilation status for modules with non-ascii names (on Windows).

* Help with remote debugging environment encoding problems in test runs, by extending the output of the "buildenv" pseudo-test.

* Explicitly set I/O encoding for subprocesses in parallel cythonize() runs to make the test runner workers inherit it (instead of defaulting to ASCII in Py2).

* Use a Latin-1 Unicode character in the test for Unicode module names to make it more compatible with Windows file system character sets (such as CP-1252).

* Properly decode source and module file name from the FS encoding in Py2. Previously, with ASCII module names, UTF-8 decoding always worked, but wasn't correct.

* Hack around a distutils 3.[5678] bug on Windows for unicode module names.
https://bugs.python.org/issue39432

* Try to fix cython.inline() on Windows with Py3.8+ where the DLL loading requires an explicit registration of the extension output directory.
Closes GH-3450.

Reduce warning level in MSVC again since /W4 turns out to be excessive (complains about constant conditionals, for example).

Increase warning level in appveyor builds (could also use "/Wall", but let's see how spammy /W4 is).

Most are non-user facing. 
Found using:
`codespell -d -q 3`

Exclude Py3.3 from appveyor builds as it is out of maintenance anyway and isn't really supported by external packages anymore.

use compiled Cython for appveyor build: we compile it anyway so that is what we should test (and it speeds up the tests)

* Add Python 3.5 to the build matrix
* Rework helper build script (copied from mpi4py)

* Add Python 2.6 x86/x64 to the build matrix.
* Use clone_depth option, no need to clone the full repo.
* Build master branch and last release branch.
* Use up-to-date pip and setuptools.
* Build wheels, msi, and wininst installers.

Use the appveyor continuous integration service to build wheels for
windows. This procedure was adapted from this guide:

https://packaging.python.org/en/latest/appveyor.html