Fix compilation of the SFML demos

demo/sfml_opengl2/main.cpp

@@ -165,7 +165,6 @@ int main(void)
 
         /* Draw */
         win.setActive(true);
-        nk_color_fv(bg, background);
         glClear(GL_COLOR_BUFFER_BIT);
         glClearColor(bg.r, bg.g, bg.b, bg.a);
         /* IMPORTANT: `nk_sfml_render` modifies some global OpenGL state

demo/sfml_opengl2/nuklear_sfml_gl2.h

@@ -97,9 +97,9 @@ nk_sfml_render(enum nk_anti_aliasing AA)
     glEnableClientState(GL_COLOR_ARRAY);
     {
         GLsizei vs = sizeof(struct nk_sfml_vertex);
-        size_t vp = offsetof(struct nk_sfml_vertex, position);
-        size_t vt = offsetof(struct nk_sfml_vertex, uv);
-        size_t vc = offsetof(struct nk_sfml_vertex, col);
+        size_t vp = NK_OFFSETOF(struct nk_sfml_vertex, position);
+        size_t vt = NK_OFFSETOF(struct nk_sfml_vertex, uv);
+        size_t vc = NK_OFFSETOF(struct nk_sfml_vertex, col);
 
         /* convert from command queue into draw  list and draw to screen */
         const struct nk_draw_command* cmd;

demo/sfml_opengl3/main.cpp

@@ -171,9 +171,7 @@ int main(void)
         /* ----------------------------------------- */
 
         /* Draw */
-        float bg[4];
         win.setActive(true);
-        nk_color_fv(bg, background);
         glClear(GL_COLOR_BUFFER_BIT);
         glClearColor(bg.r, bg.g, bg.b, bg.a);
         /* IMPORTANT: `nk_sfml_render` modifies some global OpenGL state

demo/sfml_opengl3/nuklear_sfml_gl3.h

@@ -134,9 +134,9 @@ nk_sfml_device_create(void)
     {
         /* buffer setup */
         GLsizei vs = sizeof(struct nk_sfml_vertex);
-        size_t vp = offsetof(struct nk_sfml_vertex, position);
-        size_t vt = offsetof(struct nk_sfml_vertex, uv);
-        size_t vc = offsetof(struct nk_sfml_vertex, col);
+        size_t vp = NK_OFFSETOF(struct nk_sfml_vertex, position);
+        size_t vt = NK_OFFSETOF(struct nk_sfml_vertex, uv);
+        size_t vc = NK_OFFSETOF(struct nk_sfml_vertex, col);
 
         glGenBuffers(1, &dev->vbo);
         glGenBuffers(1, &dev->ebo);