spec: Manually specify every --enable-XXX flag we use
    
    This moves the %build section to be closer to RHEL qemu-kvm content.
    It's a bit tedious but it ensures we enable every feature we actually
    think we are enabling :)
    
    Add some macros to facilitate sharing this layout with the RHEL spec
    
    The only functional change is now we use gcrypt instead of nettle.
    I'm not sure if that was intentional before, but gcrypt is requested
    on RHEL so I'm guessing that's what we want for Fedora too
    
    Signed-off-by: Cole Robinson <crobinso@redhat.com>