UI cleanup work;

Proportional edit:

- Proportional mode added to header as button/menu. Including new option
  to have only connected geometry influenced.
- Added icons for proportional & proportional modes
- Make proportional edit data part of Scene, so all gets saved.
  The Global flag G_PROPORTIONAL was removed
- Made sure #defines get used properly, also tweaked order for proportional
  so it starts with regular 'smooth' by default.
- Use ALT+O in editmode to switch to new proportional 'connected' mode

Other UI stuff:

- in EditMode, the layer buttons get hidden... the amount of icons in
  3d header grows to fast. :)
- made less ugly icons for the Manipulators. Still can be better.
- Added alpha-filter for pre-processing Icon-image, giving nicer display
  of icon-antialising on dark or bright backdrops
- disabled Manipulators when in editmode, and current layers don't show
  the edited data.
- Added the value used to define Normal size (editmode draw) in Scene too,
  so it gets saved.

source/blender/src/space.c

@@ -1462,12 +1462,16 @@ static void winqreadview3dspace(ScrArea *sa, void *spacedata, BWinEvent *evt)
 				ob= OBACT;
 				if (G.obedit) {
 					if (G.qual==LR_SHIFTKEY) {
-						extern int prop_mode;
-						prop_mode = (prop_mode+1)%6;
+						G.scene->prop_mode = (G.scene->prop_mode+1)%6;
+						allqueue(REDRAWHEADERS, 0);
+					}
+					else if((G.qual==LR_ALTKEY)) {
+						if(G.scene->proportional==2) G.scene->proportional= 1;
+						else G.scene->proportional= 2;
 						allqueue(REDRAWHEADERS, 0);
 					}
 					else if((G.qual==0)) {
-						G.f ^= G_PROPORTIONAL;
+						G.scene->proportional= !G.scene->proportional;
 						allqueue(REDRAWHEADERS, 0);
 					}
 				}
@@ -3825,14 +3829,10 @@ static void winqreadimagespace(ScrArea *sa, void *spacedata, BWinEvent *evt)
 				break;
 			case OKEY:
 				if (G.qual==LR_SHIFTKEY) {
-					extern int prop_mode;
-					prop_mode= !prop_mode;
+					G.scene->prop_mode= !G.scene->prop_mode;
 				}
 				else if((G.qual==0)) {
-					if(G.f & G_PROPORTIONAL)
-						G.f &= ~G_PROPORTIONAL;
-					else
-						G.f |= G_PROPORTIONAL;
+					G.scene->proportional= !G.scene->proportional;
 				}
 				break;
 			case PKEY: