Now that we have C and C++, we need to split the compile and link steps
(because we need different flags for the C and C++ files), so this is
easier with a Makefile.

Replace the python scripts for building the shared lib and tests with a
Makefile, which makes it easier to handle a mix of C and C++.

Rename axolotlpp as olm to avoid confusion with Axolotl-the-spec and Axolotl-the-OWS-libraries at moxie's request