Merge branch 'master' into tls

Conflicts:
	src/x11_window.c

src/opengl.c

@@ -508,7 +508,7 @@ GLFWAPI GLFWwindow glfwGetCurrentContext(void)
     if (!_glfwInitialized)
     {
         _glfwSetError(GLFW_NOT_INITIALIZED, NULL);
-        return GL_FALSE;
+        return NULL;
     }
 
     return _glfwPlatformGetCurrentContext();