glx/windows: Add stdbool.h include to 'direct GLX via WGL' implementation

These files make use of the constant 'false', but don't include
stdbool.h.

Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41421>

src/glx/windows/wgl.c

@@ -28,6 +28,7 @@
 #include "wgl.h"
 
 #include <stdio.h>
+#include <stdbool.h>
 
 #define RESOLVE_DECL(type) \
     static type type##proc = NULL;

src/glx/windows/windows_drawable.c

@@ -27,6 +27,7 @@
 #include "wgl.h"
 
 #include <stdio.h>
+#include <stdbool.h>
 
 /*
  * Window drawable