Added help entries for anim functions. Fixed a compilation warning and a wrong anim button refresh.

git-svn-id: svn://pulkomandy.tk/GrafX2/trunk@1854 416bcca6-2ee7-4201-b75f-2eb2f807beb1

src/layers.c

@@ -644,6 +644,6 @@ void Button_Anim_continuous_prev(void)
   } while (Mouse_K);
 
   Hide_cursor();
-  Unselect_button(BUTTON_ANIM_NEXT_FRAME);
+  Unselect_button(BUTTON_ANIM_PREV_FRAME);
   Display_cursor();
 }