Add GLFW_NO_API for creating context-less windows

include/GLFW/glfw3.h

@@ -613,6 +613,15 @@ extern "C" {
  *  the user, as appropriate.
  */
 #define GLFW_FORMAT_UNAVAILABLE     0x00010009
+/*! @brief The specified window does not have an OpenGL or OpenGL ES context.
+ *
+ *  A window that does not have an OpenGL or OpenGL ES context was passed to
+ *  a function that requires it to have one.
+ *
+ *  @par Analysis
+ *  Application programmer error.  Fix the offending call.
+ */
+#define GLFW_NO_WINDOW_CONTEXT      0x0001000A
 /*! @} */
 
 #define GLFW_FOCUSED                0x00020001
@@ -650,6 +659,7 @@ extern "C" {
 #define GLFW_OPENGL_PROFILE         0x00022008
 #define GLFW_CONTEXT_RELEASE_BEHAVIOR 0x00022009
 
+#define GLFW_NO_API                          0
 #define GLFW_OPENGL_API             0x00030001
 #define GLFW_OPENGL_ES_API          0x00030002