Drop the lightning subpackage
    
    This causes headaches during package updates for the main package
    Additionally, it's got its own release schedule independent of the
    Thunderbird release schedule and including two such things in a
    single SRPM is just a recipe for disaster.  Lightning needs to be
    packaged up in a separate SRPM.
    
    This is being done in https://bugzilla.redhat.com/show_bug.cgi?id=693493
    
    Conflicts:
    
    	thunderbird.spec