Wayland: Make libwayland-client dynamically loaded

The insight to use wayland.xml to resolve the difficult-to-redirect
interface symbols was gleaned from SDL.

Instead of compiling the code output of wayland-scanner separately it is
made part of the wl_init compilation unit.  This lets us do things like
transparently rename our copies of Wayland globals.

The OS version of wayland-client-protocol.h is no longer used by GLFW,
but it is presumably ABI compatible with the output of wayland-scanner.

Closes #1174.
Closes #1338.
Related to #1655.
Closes #1943.

src/wl_monitor.c

@@ -34,6 +34,8 @@
 #include <errno.h>
 #include <math.h>
 
+#include "wayland-client-protocol.h"
+
 
 static void outputHandleGeometry(void* data,
                                  struct wl_output* output,