Refactor folder (#10475)

Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.

deps_src/libigl/igl/opengl/glfw/background_window.h

@@ -0,0 +1,34 @@
+#ifndef IGL_OPENGL_GLFW_BACKGROUND_WINDOW_H
+#define IGL_OPENGL_GLFW_BACKGROUND_WINDOW_H
+#include "../../igl_inline.h"
+
+#include "../gl.h"
+#include <GLFW/glfw3.h>
+
+namespace igl
+{
+  namespace opengl
+  {
+    namespace glfw
+    {
+      // Create a background window with a valid core profile opengl context
+      // set to current.
+      //
+      // After you're finished with this window you may call
+      // `glfwDestroyWindow(window)`
+      //
+      // After you're finished with glfw you should call `glfwTerminate()`
+      //
+      // Outputs:
+      //    window  pointer to glfw window
+      // Returns true iff success
+      IGL_INLINE bool background_window(GLFWwindow* & window);
+    }
+  }
+}
+
+#ifndef IGL_STATIC_LIBRARY
+#  include "background_window.cpp"
+#endif
+
+#endif