Use internal temp variable for swap macros. Make swaps/swapl type safe (introducing wrong_size check at build time).

 While working on this changeset, various spots got discovered where
 swapl or swaps was used on a wrong type, where byte swapping calls had
 been forgotten or done on the wrong variable.

 This backport at least includes changes from the following X.org
 commits, listed in non-chronological order:

 commit 2c7c520cfe0df30f4bc3adba59d9c62582823bf8
 Author: Matt Turner <mattst88@gmail.com>
 Date:   Thu Aug 4 15:35:41 2011 -0400

    Use internal temp variable for swap macros

    Also, fix whitespace, mainly around
        swaps(&rep.sequenceNumber)
Reviewed-by: Peter Harris <pharris@opentext.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>

 commit 9edcae78c46286baff42e74bfe26f6ae4d00fe01
 Author: Matt Turner <mattst88@gmail.com>
 Date:   Wed Sep 21 17:14:16 2011 -0400

    Use correct swap{l,s} (or none at all for CARD8)

    Swapping the wrong size was never caught because swap{l,s} are macros.

    It's clear in the case of Xext/xres.c, that the author believed
    client_major/minor to be CARD16 from looking at the code in the first
    hunk.

    v2: dmx.c fixes from Keith.
Reviewed-by: Peter Harris <pharris@opentext.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>

 commit dab064fa5e0b1f5c67222562ad5367005832cba1
 Author: Andrea Canciani <ranma42@gmail.com>
 Date:   Tue Nov 2 20:10:32 2010 +0100

    render: Fix byteswapping of gradient stops

    The function swapStops repeatedly swaps the color components as
    CARD16, but incorrectly steps over them as if they were CARD32.

    This causes half of the stops not to be swapped at all and some
    unrelated data be swapped instead.
Signed-off-by: Andrea Canciani <ranma42@gmail.com>
Reviewed-by: Soren Sandmann <sandmann@daimi.au.dk>
Reviewed-by: Julien Cristau <jcristau@debian.org>
Signed-off-by: Keith Packard <keithp@keithp.com>

 commit 54770c980cd2b91a8377f975a58ed69def5cfa42
 Author: Matt Turner <mattst88@gmail.com>
 Date:   Tue Aug 16 16:59:07 2011 -0400

    Cast char* buffers to swap functions
Reviewed-by: Peter Harris <pharris@opentext.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>

 commit 6844bd2e63490870bab3c469eec6030354ef2865
 Author: Alan Coopersmith <alan.coopersmith@sun.com>
 Date:   Wed Jan 9 19:52:00 2008 -0800

    More Xv extension byte swapping fixes

 commit e46f6ddeccd082b2d507a1e8b57ea30e6b0a2c83
 Author: Michel Dänzer <michel@tungstengraphics.com>
 Date:   Wed Jan 16 14:24:22 2008 +0100

    Yet another Xv extension byte swapping fix.