drop obsolete XAA

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: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/driver/xf86-video-sis/-/merge_requests/26>

configure.ac

@@ -107,24 +107,6 @@ if test "$DRI" = yes; then
         AC_DEFINE(SISDRI_DEVEL,1,[Enable developmental DRI driver support])
 fi
 
-AC_ARG_ENABLE(xaa,
-              AS_HELP_STRING([--enable-xaa],
-                             [Enable legacy X Acceleration Architecture (XAA) [default=auto]]),
-              [XAA="$enableval"],
-              [XAA=auto])
-if test "x$XAA" != xno; then
-        save_CFLAGS=$CFLAGS
-        save_CPPFLAGS=$CPPFLAGS
-        CFLAGS=$XORG_CFLAGS
-        CPPFLAGS="$XORG_CFLAGS"
-        AC_CHECK_HEADERS([xaa.h], XAA=yes, XAA=no)
-        CFLAGS=$save_CFLAGS
-        CPPFLAGS=$save_CPPFLAGS
-fi
-AC_MSG_CHECKING([whether to include XAA support])
-AM_CONDITIONAL(XAA, test "x$XAA" = xyes)
-AC_MSG_RESULT([$XAA])
-
 # technically this should be a configure flag.  meh.
 AC_DEFINE(USE_EXA, 1, [Build support for EXA])