Mostly done via unifdef -UHAVE_XAA_H, followed by minor manual editing

Since recent commits require xserver-1.18.0 or later to build against,
there's no reason leaving behind big chunks of code that can only build
against the XAA support removed in xserver-1.13.0 (released in 2012).

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
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