Pythia8_i: Fixes for some old cmt code.
Don't rely on the PYTHIA8_VERSION cmake variable --- it can be set wrong. Instead, get the version from PYTHIA8_INCLUDE_DIR.
Remove some old CMT-dependent code.
Don't rely on the PYTHIA8_VERSION cmake variable --- it can be set wrong. Instead, get the version from PYTHIA8_INCLUDE_DIR.
Remove some old CMT-dependent code.