Use Imgui integrated opengl loader

libs/imgui/backends/imgui_impl_opengl3.cpp

@@ -139,7 +139,7 @@
 // - You can temporarily use an unstripped version. See https://github.com/dearimgui/gl3w_stripped/releases
 // Changes to this backend using new APIs should be accompanied by a regenerated stripped loader version.
 #define IMGL3W_IMPL
-#include <GL/glew.h>
+#include "imgui_impl_opengl3_loader.h"
 #endif
 
 // Vertex arrays are not supported on ES2/WebGL1 unless Emscripten which uses an extension
@@ -236,9 +236,14 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
     ImGuiIO& io = ImGui::GetIO();
     IM_ASSERT(io.BackendRendererUserData == NULL && "Already initialized a renderer backend!");
 
-
     // Initialize our loader
-	glewInit();
+#if !defined(IMGUI_IMPL_OPENGL_ES2) && !defined(IMGUI_IMPL_OPENGL_ES3) && !defined(IMGUI_IMPL_OPENGL_LOADER_CUSTOM)
+    if (imgl3wInit() != 0)
+    {
+        fprintf(stderr, "Failed to initialize OpenGL loader!\n");
+        return false;
+    }
+#endif
 
     // Setup backend capabilities flags
     ImGui_ImplOpenGL3_Data* bd = IM_NEW(ImGui_ImplOpenGL3_Data)();
@@ -258,13 +263,6 @@ bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
         sscanf(gl_version, "%d.%d", &major, &minor);
     }
     bd->GlVersion = (GLuint)(major * 100 + minor * 10);
-
-    // Query vendor to enable glBufferSubData kludge
-#ifdef _WIN32
-    if (const char* vendor = (const char*)glGetString(GL_VENDOR))
-        if (strncmp(vendor, "Intel", 5) == 0)
-            bd->UseBufferSubData = true;
-#endif
     //printf("GL_MAJOR_VERSION = %d\nGL_MINOR_VERSION = %d\nGL_VENDOR = '%s'\nGL_RENDERER = '%s'\n", major, minor, (const char*)glGetString(GL_VENDOR), (const char*)glGetString(GL_RENDERER)); // [DEBUG]
 #else
     bd->GlVersion = 200; // GLES 2