[Feat|Fix|Improvement] (All): Continue building the basic structure.

Feat: implement MG_Impl/Buffer
Feat: implement MG_State/ErrorState and integrate it into MG_State/GLContext
Feat: add buffer deletion management
Feat: introduce `INSERTION_POINT` (https://github.com/MobileGL-Dev/MobileGLCodeManager)
Feat: add tests about MG_Impl/Buffer and buffer deletion feature
Feat: add several converters
Fix: fix some compiling errors
Fix: fix some incorrect behaviors in MG_State/Buffer
Improvement: remove some current statements at the beginning of the source file, which will be added uniformly soon
Improvement: optimize some naming

MobileGL/MG_State/GLState/Core.cpp

@@ -3,20 +3,66 @@
 namespace MobileGL {
     namespace MG_State {
         namespace GLState {
+            // Error
+            void GLContext::RecordError(ErrorCode code, SharedPtr<ErrorInfo> info) {
+                m_errorState.RecordError(code, info);
+            }
+
+            bool GLContext::HasGLError() const {
+                return m_errorState.HasGLError();
+            }
+
+            Optional<const Error> GLContext::PeekGLError() const {
+                return m_errorState.PeekGLError();
+            }
+
+            Optional<Error> GLContext::PopGLError() {
+                return m_errorState.PopGLError();
+            }
+
+            bool GLContext::HasNonGLError() const {
+                return m_errorState.HasNonGLError();
+            }
+
+            Optional<const Error> GLContext::PeekNonGLError() const {
+                return m_errorState.PeekNonGLError();
+            }
+
+            Optional<Error> GLContext::PopNonGLError() {
+                return m_errorState.PopNonGLError();
+            }
+
+            void GLContext::ClearErrors() {
+                m_errorState.Clear();
+            }
+
+			// Buffer
             Vector<Uint> GLContext::GenBufferNames(Uint number) {
-                return bufferState_.GenerateNames(number);
+                return m_bufferState.GenerateNames(number);
             }
 
             SharedPtr<BufferObject> GLContext::GetBufferObject(Uint index) {
-                return bufferState_.GetBufferObject(index);
+                return m_bufferState.GetBufferObject(index);
             }
 
             BindingSlot<BufferObject>& GLContext::GetBufferBindingSlot(BufferTarget target) {
-                return bufferState_.GetBindingSlot(target);
+                return m_bufferState.GetBindingSlot(target);
             }
 
             SharedPtr<BufferObject> GLContext::CreateBufferObject(Uint index) {
-                return bufferState_.CreateBufferObject(index);
+                return m_bufferState.CreateBufferObject(index);
+            }
+
+            void GLContext::MarkBufferObjectForDeletion(Uint index) {
+                m_bufferState.MarkBufferObjectForDeletion(index);
+            }
+
+            bool GLContext::ValidateBufferName(Uint index) const {
+				return m_bufferState.ValidateName(index);
+            }
+
+            bool GLContext::ValidateBufferObject(Uint index) const {
+				return m_bufferState.ValidateBufferObject(index);
             }
 
         }