Added channel bit depth hint defaults.

src/window.c

@@ -84,6 +84,12 @@ void _glfwSetDefaultWindowHints(void)
 
     // The default is to allow window resizing
     _glfwLibrary.hints.resizable = GL_TRUE;
+
+    // The default is 24 bits of depth, 8 bits of color
+    _glfwLibrary.hints.depthBits = 24;
+    _glfwLibrary.hints.redBits   = 8;
+    _glfwLibrary.hints.greenBits = 8;
+    _glfwLibrary.hints.blueBits  = 8;
 }