Patch to check XRender correctly with Cairo backend

[Yen-Ju Chen]

Here is a patch to check XRender with Cairo backend.
The main bug is that configure.ac need to know the backend when
checking XRender. But backend is only decided in the end.
So XRender always fails.
The patch may not be perfect because I don't know exact where to move the code.

Yen-Ju

Index: configure.ac
===================================================================
--- configure.ac        (revision 25449)
+++ configure.ac        (working copy)
@@ -377,13 +377,13 @@

 have_xrender=no
 AC_CHECK_LIB(Xrender, XRenderFindVisualFormat, have_xrender=yes)
-if test "$have_xrender" = yes; then
-  # we'll use it only if we want cairo
-  if test x"$BUILD_GRAPHICS" = "xcairo"; then
-    AC_DEFINE(XRENDER,1,[Define if you have X11 XRender extension])
-    LIBS="$LIBS -lXrender"
-  fi
-fi
+#if test "$have_xrender" = yes; then
+#  # we'll use it only if we want cairo
+#  if test x"$BUILD_GRAPHICS" = "xcairo"; then
+#    AC_DEFINE(XRENDER,1,[Define if you have X11 XRender extension])
+#    LIBS="$LIBS -lXrender"
+#  fi
+#fi

 #--------------------------------------------------------------------
 # Glitz libraries
@@ -569,6 +569,14 @@
   fi
 fi

+if test "$have_xrender" = yes; then
+  # we'll use it only if we want cairo
+  if test x"$BUILD_GRAPHICS" = "xcairo"; then
+    AC_DEFINE(XRENDER,1,[Define if you have X11 XRender extension])
+    LIBS="$LIBS -lXrender"
+  fi
+fi
+
 AH_TOP([
 #define SERVER_x11   1
 #define SERVER_win32 2