Removed unused struct member.

src/internal.h

@@ -177,7 +177,6 @@ struct _GLFWwindow
     GLboolean closeRequested;  // GL_TRUE if this window should be closed
     int       width, height;
     int       positionX, positionY;
-    int       mode;            // GLFW_WINDOWED or GLFW_FULLSCREEN
     GLboolean resizable;       // GL_TRUE if user may resize this window
     GLboolean visible;         // GL_TRUE if this window is visible
     void*     userPointer;