This test case demonstrates a bug, where automodule:: with option
:members: fails to document a class attribute of a class, that was
imported into the documented module.
This commit extends test_ext_viewcode, instead of creating a separate
test module, because the development guide recommends it for performance
reasons.
* rename a few test modules to make the names more consistent
* do not copy/use Sphinx from build/ (unnecessary without 2to3)
* use a temporary dir for *all* test projects, the source tree
will stay pristine that way (default is tests/build)
* speed up tests by ~3x by splitting up test projects and avoiding
rebuilds
