Use PY_VERSION_HEX to simplify conditional compilation depending on the Python version. This also adds a static_assert to lldb-python to error out with a meaningful diagnostic when you try building LLDB with an older Python version in preparation for [1]. [1] https://discourse.llvm.org/t/rfc-lets-document-and-enforce-a-minimum-python-version-for-lldb/82731/15