Misc #218: Warn about using --glx-no-rebind-pixmap on intel driver

Warn about using --glx-no-rebind-pixmap on xf86-video-intel. Thanks to
aktau for the info. (#218)

compton.c

@@ -4682,7 +4682,8 @@ usage(int ret) {
     "--glx-no-rebind-pixmap\n"
     "  GLX backend: Avoid rebinding pixmap on window damage. Probably\n"
     "  could improve performance on rapid window content changes, but is\n"
-    "  known to break things on some drivers.\n"
+    "  known to break things on some drivers (LLVMpipe, xf86-video-intel,\n"
+    "  etc.).\n"
     "--glx-swap-method undefined/copy/exchange/3/4/5/6/buffer-age\n"
     "  GLX backend: GLX buffer swap method we assume. Could be\n"
     "  undefined (0), copy (1), exchange (2), 3-6, or buffer-age (-1).\n"