Try and get more detailed Firefox logs from startx
    
    When we run Firefox directly on X lately, we often hit a bug
    where X just suddenly exits in the middle of doing stuff in
    Firefox. I'm not sure if this is a bug in X or in Firefox (if
    Firefox crashed, X would immediately exit). Let's see if this
    helps get any info on what's going on with Firefox.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>