X11: Try to load libXrandr.so.3 if libXrandr.so.2 isn't found

All Linux distros, and FreeBSD and OpenBSD seem to have libXrandr.so.2,
but for some reason recent NetBSD versions seem to have libXrandr.so.3 now.

(cherry picked from commit 413ff7938df54c6c0bf6dc3ecd86c2c713f6f43a)

platform/x11/os_x11.cpp

@@ -163,7 +163,12 @@ Error OS_X11::initialize(const VideoMode &p_desired, int p_video_driver, int p_a
 	xrandr_handle = dlopen("libXrandr.so.2", RTLD_LAZY);
 	if (!xrandr_handle) {
 		err = dlerror();
-		fprintf(stderr, "could not load libXrandr.so.2, Error: %s\n", err);
+		// For some arcane reason, NetBSD now ships libXrandr.so.3 while the rest of the world has libXrandr.so.2...
+		// In case this happens for other X11 platforms in the future, let's give it a try too before failing.
+		xrandr_handle = dlopen("libXrandr.so.3", RTLD_LAZY);
+		if (!xrandr_handle) {
+			fprintf(stderr, "could not load libXrandr.so.2, Error: %s\n", err);
+		}
 	} else {
 		XRRQueryVersion(x11_display, &xrandr_major, &xrandr_minor);
 		if (((xrandr_major << 8) | xrandr_minor) >= 0x0105) {