x: use modifier-aware buffer import

wire-xcon/dri3.txt

@@ -29,3 +29,25 @@ request Dri3PixmapFromBuffer = 2 (
     bpp: u8,
     pixmap_fd: fd,
 );
+
+request Dri3PixmapFromBuffers = 7 (
+    pixmap: u32,
+    window: u32,
+    num_buffers: u8,
+    @pad 3,
+    width: u16,
+    height: u16,
+    stride0: u32,
+    offset0: u32,
+    stride1: u32,
+    offset1: u32,
+    stride2: u32,
+    offset2: u32,
+    stride3: u32,
+    offset3: u32,
+    depth: u8,
+    bpp: u8,
+    @pad 2,
+    modifier: u64,
+    buffers: list(fd, field(num_buffers)),
+);