Workaround an xcb-dri2 bug.

xcb_dri2_connect_device_name generated by xcb-proto 1.6 is broken.  It
only works when the length of the driver name is a multiple of 4.

compositor/compositor-x11.c

@@ -16,6 +16,10 @@
  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -152,9 +156,22 @@ dri2_connect(struct x11_compositor *c)
 		return -1;
 	}
 
+#ifdef XCB_DRI2_CONNECT_DEVICE_NAME_BROKEN
+	{
+		char *driver_name, *device_name;
+
+		driver_name = xcb_dri2_connect_driver_name (connect);
+		device_name = driver_name +
+			((connect->driver_name_length + 3) & ~3);
+		snprintf(path, sizeof path, "%.*s",
+			 xcb_dri2_connect_device_name_length (connect),
+			 device_name);
+	}
+#else
 	snprintf(path, sizeof path, "%.*s",
 		 xcb_dri2_connect_device_name_length (connect),
 		 xcb_dri2_connect_device_name (connect));
+#endif
 	free(connect);
 
 	fd = open(path, O_RDWR);

configure.ac

@@ -34,6 +34,11 @@ AC_CHECK_LIB(expat, XML_ParserCreate, [EXPAT_LIBS="-lexpat"],
 	     [AC_MSG_ERROR([Can't find expat library. Please install expat.])])
 AC_SUBST(EXPAT_LIBS)
 
+# workaround a bug in xcb-dri2 generated by xcb-proto 1.6
+AC_CHECK_LIB(xcb-dri2, xcb_dri2_connect_alignment_pad, [],
+	     [AC_DEFINE([XCB_DRI2_CONNECT_DEVICE_NAME_BROKEN], [1],
+			[Define to 1 if xcb_dri2_connect_device_name is broken])])
+
 AC_CONFIG_FILES([wayland/wayland-server.pc
 		 wayland/wayland-client.pc
 		 Makefile