Patch From: Hugh Dickins <hugh@veritas.com>

Recently noticed that __GFP_HIGHIO has played no real part since bounce
buffering was converted to mempool in 2.5.12: so this patch (over 2.5.58-mm1)
removes it and GFP_NOHIGHIO and SLAB_NOHIGHIO.

Also removes GFP_KSWAPD, in 2.5 same as GFP_KERNEL; leaves GFP_USER, which
can be a useful comment, even though in 2.5 same as GFP_KERNEL.

One anomaly needs comment: strictly, if there's no __GFP_HIGHIO, then
GFP_NOHIGHIO translates to GFP_NOFS; but GFP_NOFS looks wrong in the block
layer, and if you follow them down, you find that GFP_NOFS and GFP_NOIO
behave the same way in mempool_alloc - so I've used the less surprising
GFP_NOIO to replace GFP_NOHIGHIO.