Added the possibility to use DGA 2.0.

diff --git a/configure.in b/configure.in
index 912c1fc..3463b77 100644
--- a/configure.in
+++ b/configure.in
@@ -130,10 +130,11 @@
     then 
         AC_CHECK_LIB(Xext,XShmQueryExtension,AC_DEFINE(HAVE_LIBXXSHM),,$X_LIBS -lXext -lX11)
     fi
-    dnl Check for XFree86 DGA extension
+    dnl Check for XFree86 DGA / DGA 2.0 extension
     AC_CHECK_HEADERS(X11/Xlib.h X11/extensions/xf86dga.h)
     if test "$ac_cv_header_X11_Xlib_h" = "yes" -a "$ac_cv_header_X11_extensions_xf86dga_h" = "yes"
     then 
+         AC_CHECK_LIB(Xxf86dga,XDGAQueryExtension,AC_DEFINE(HAVE_LIBXXF86DGA2) X_PRE_LIBS="$X_PRE_LIBS -lXxf86dga",,$X_LIBS -lXext -lX11)
          AC_CHECK_LIB(Xxf86dga,XF86DGAQueryExtension,AC_DEFINE(HAVE_LIBXXF86DGA) X_PRE_LIBS="$X_PRE_LIBS -lXxf86dga",,$X_LIBS -lXext -lX11)
     fi