Doxygen documentation of global.h and const.h (in English)

Some small changes in code that don't change the generated executable:
- 4 constants that were #defined are now enums, so they automatically get the right value: NB_ICON_SPRITES, NB_BUTTONS, NB_SPECIAL_SHORTCUTS, NB_OPERATIONS.
- Some numeric constants replaced by their symbolic value.


git-svn-id: svn://pulkomandy.tk/GrafX2/trunk@750 416bcca6-2ee7-4201-b75f-2eb2f807beb1

misc.c

@@ -224,6 +224,7 @@ void Replace_a_color(byte old_color, byte New_color)
   Update_rect(0,0,0,0); // On peut TOUT a jour
   // C'est pas un problème car il n'y a pas de preview
 }
+// FIXME: move to graph.c, it's the only caller
 
 void Ellipse_compute_limites(short horizontal_radius,short vertical_radius)
 {
@@ -234,6 +235,7 @@ void Ellipse_compute_limites(short horizontal_radius,short vertical_radius)
   Ellipse_limit = Ellipse_horizontal_radius_squared * Ellipse_vertical_radius_squared;
 }
 
+// FIXME: move to graph.c, it's the only caller
 byte Pixel_in_ellipse(void)
 {
   qword ediesi = Ellipse_cursor_X * Ellipse_cursor_X * Ellipse_vertical_radius_squared +
@@ -243,6 +245,7 @@ byte Pixel_in_ellipse(void)
         return 0;
 }
 
+// FIXME: move to graph.c, it's the only caller
 byte Pixel_in_circle(void)
 {
         if(Circle_cursor_X * Circle_cursor_X +