Sync up kernel configs for x86/x86_64 flavors.
    
    The idea is that the other flavors should be based on nearly identical
    configs with the only differences between them directly related to the
    topic of the flavor.
    
    For x86_64, kernel-default is the base, and everything else is based on
    that. X86 uses kernel-pae as the base, and that is derived by copying
    the x86_64 -default kernel and enabling ISA drivers and PAE.
    
    The other architectures need work, but I'd prefer experts on those
    architectures do that work instead.