Null: Make platform more conformant

This makes the null platform behave more like an actual stub.  More
queryable state is tracked and there is even a fake monitor with one
whole fake video mode.

src/null_platform.h

@@ -27,12 +27,12 @@
 
 #include <dlfcn.h>
 
-#define _GLFW_PLATFORM_WINDOW_STATE _GLFWwindowNull null
+#define _GLFW_PLATFORM_WINDOW_STATE         _GLFWwindowNull null
+#define _GLFW_PLATFORM_LIBRARY_WINDOW_STATE _GLFWlibraryNull null
+#define _GLFW_PLATFORM_MONITOR_STATE        _GLFWmonitorNull null
 
 #define _GLFW_PLATFORM_CONTEXT_STATE         struct { int dummyContext; }
-#define _GLFW_PLATFORM_MONITOR_STATE         struct { int dummyMonitor; }
 #define _GLFW_PLATFORM_CURSOR_STATE          struct { int dummyCursor; }
-#define _GLFW_PLATFORM_LIBRARY_WINDOW_STATE  struct { int dummyLibraryWindow; }
 #define _GLFW_PLATFORM_LIBRARY_CONTEXT_STATE struct { int dummyLibraryContext; }
 #define _GLFW_EGL_CONTEXT_STATE              struct { int dummyEGLContext; }
 #define _GLFW_EGL_LIBRARY_CONTEXT_STATE      struct { int dummyEGLLibraryContext; }
@@ -56,7 +56,37 @@
 //
 typedef struct _GLFWwindowNull
 {
-    int width;
-    int height;
+    int             xpos;
+    int             ypos;
+    int             width;
+    int             height;
+    char*           title;
+    GLFWbool        visible;
+    GLFWbool        iconified;
+    GLFWbool        maximized;
+    GLFWbool        resizable;
+    GLFWbool        decorated;
+    GLFWbool        floating;
+    GLFWbool        transparent;
+    float           opacity;
 } _GLFWwindowNull;
 
+// Null-specific per-monitor data
+//
+typedef struct _GLFWmonitorNull
+{
+    GLFWgammaramp   ramp;
+} _GLFWmonitorNull;
+
+// Null-specific global data
+//
+typedef struct _GLFWlibraryNull
+{
+    int             xcursor;
+    int             ycursor;
+    char*           clipboardString;
+    _GLFWwindow*    focusedWindow;
+} _GLFWlibraryNull;
+
+void _glfwPollMonitorsNull(void);
+