First commit of a new toolbox system.

Aim was to find a simple & easy system, script alike, to add and configure
a toolbox system, so that others can experiment, but also of course Python.

Summary:
- spacebar calls it up. SHIFT+A still does old toolbox
- hold left or rightmouse for 0.4 second, and it pops up as well
  this is experimental! Can be tweaked with Userdef var "ThresA"
- it is a little bit complete for Object mode only. Needs still work
  at information desing/structure level
- the code works like an engine, interpreting structs like this:

static TBitem addmenu_curve[]= {
{	0, "Bezier Curve", 	0, NULL},
{	0, "Bezier Circle", 1, NULL},
{	0, "NURBS Curve", 	2, NULL},
{	0, "NURBS Circle", 	3, NULL},
{	0, "Path", 			4, NULL},
{  -1, "", 			0, do_info_add_curvemenu}};

- first value is ICON code,
- then name
- return value
- pointer to optional child

last row has -1 to indicate its the last...
plus a callback to event function.

I also built an old toolbox style callback for this:

static TBitem tb_object_select[]= {
{	0, "Border Select|B", 	'b', NULL},
{	0, "(De)select All|A", 	'a', NULL},
{	0, "Linked...|Shift L", 	'L', NULL},
{	0, "Grouped...|Shift G", 	'G', NULL},
{  -1, "", 			0, tb_do_hotkey}};

here the return values are put back as hotkeys in mainqueue.

A mainloop can do all context switching, and build menus on the fly.
Meaning, it also allows other designs such as radials...

source/blender/include/BSE_headerbuttons.h

@@ -105,4 +105,11 @@ void do_view3d_buttons(short event);
 
 void do_headerbuttons(short event);
 
+/* header_info.c */
+void do_info_add_meshmenu(void *arg, int event);
+void do_info_add_curvemenu(void *arg, int event);
+void do_info_add_surfacemenu(void *arg, int event);
+void do_info_add_metamenu(void *arg, int event);
+void do_info_addmenu(void *arg, int event);
+
 #endif /*  BSE_HEADERBUTTONS_H */