* python3.8: bulk removal of now obsolete "_python38" packages.
Done via scripting. No functional change intended or expected.
Some manual tweaks will follow.
* python3.8: further manual tweaks after bulk-3.8-removal.
Unlike the previous commit with automated changes,
I've tested builds for *these* recipes in beta4 64 bits.
Until now, INSTALL was doing both the build and the installation.
But this was bad because INSTALL was cleaning the build directory
of the python subpackage in order to build the python3 subpackage.
Creating separate build trees for each of the python subpackages
allows to keep both build trees. We can now use a TEST function.
