[Chore] (MG_Impl/Framebuffer, MG_Impl/RenderState): move ReadBuffer to the right place

MobileGL/MG_Impl/GLImpl/Framebuffer/GL_Framebuffer.cpp

@@ -304,6 +304,10 @@ namespace MobileGL {
             }
         }
 
+        void ReadBuffer_State(GLenum src) {
+            // TODO: implement
+        }
+
         void DeleteRenderbuffers_State(GLsizei n, const GLuint* renderbuffers) {
             if (n < 0) {
                 MG_State::pGLContext->RecordError(
@@ -575,6 +579,10 @@ namespace MobileGL {
             DrawBuffers_State(n, bufs);
         }
 
+        void ReadBuffer(GLenum src) {
+            ReadBuffer_State(src);
+        }
+
         void DeleteRenderbuffers(GLsizei n, const GLuint* renderbuffers) {
             DeleteRenderbuffers_State(n, renderbuffers);
         }