Closes #1427 

Move back to a matrix setup in travis.yml to avoid the long list of redundant and boring Python build setups.

* Support Pythran shape

Through a conversion to array. I've tested that and it's ok performance wise,
the C++ compiler can deal with the abstraction (with a small overhead though).

This manifests as function-type-mismatch sanitization error on Clang.

Closes GH-3238

Closes GH-3238

Blacklists failing test for now

* Allow overriding the reading of utilities files.

Add set_read_utitlities_hook() to override how utilities
files are accessed.

This change simplifies how Cython can be packaged into a single
file binary executable, where utility files are stored inside the
binary executable as package resource.

0.11.2 is over a decade old at this point so people aiming to install
  earlier versions should probably just read the documentation for those
version. There aren't any footnotes in the documentation.

Annotations are now dealt with according to PEP-563 - they are
saved as strings, rather than evaluated as Python objects.
They can/are still be used by Cython for typing.
Previous behaviour for evaluating them as Python objects was
convoluted and has been removed entirely, which hopefully doesn't
break too much.

Remove legacy imports from IPython integration since the "py3compat" module changed in IPython 7.11. (GH-3297)

Make an import prefer Py3 over Py2, since that's what most people are (or should be) using these days.

Import "Iterable" ABC class from "collections.abc" in Py3 instead of deprecated "collections" package.

Closes GH-3246.

Instead of overriding "build_ext.build_extensions()" in "old_build_ext", which works differently for parallel and sequential builds, override only "check_extensions_list()", which gets called by it at the beginning.

Import Cython in "build_ext" only if it's actually needed, i.e. if any Cython implemented extension modules were found.

Simplify the utility code loading by requiring the source file to be named explicitly. It was almost always passed anyway, so having a non-trivial search algorithm in place for a rare case of unnecessary laziness is just code bloat. (GH-3280)