Change version extra string again.
    
    Version numbers will now be displayed like this:
    
    $ guestfish --version
    guestfish 1.13.11fedora=17,release=1.fc17
    
    or in long form:
    
    $ guestfish version
    major: 1
    minor: 13
    release: 11
    extra: fedora=17,release=1.fc17
    (cherry picked from commit 8a0d18d961d66d2719134db22085928cbaab28b4)