-Codechange: Deduplicate calls to CreateEffectVehicleRel for vehicle visual effects.

git-svn-id: svn://svn.openttd.org@26745 6aa0318a-3be1-0310-93fa-89fd2396df07
-Codechange: Separate enums for visual effect type and spawning model.

git-svn-id: svn://svn.openttd.org@26746 6aa0318a-3be1-0310-93fa-89fd2396df07
-Feature: [NewGRF] Advanced visual effects with multiple effect sprites independent of spawning model.

git-svn-id: svn://svn.openttd.org@26747 6aa0318a-3be1-0310-93fa-89fd2396df07