Armature "Envelope" editing.

For defining the deformation distances of Bones, three values are being
used now. The bone tip and root radius define the bone-shape itself and the
"dist" defines the soft area around it. A full (user) doc is in CMS here;

http://www.blender3d.org/cms/Armature_Envelopes.647.0.html

Note: todo still is allowing both Vertex Deform Groups and these Envelopes
together (and or per Bone).

Also part of this commit is:

- New: Hiding bones in EditMode. This is a separate 'hide flag', so you can
  keep the PoseMode hidden Bones separate from EditMode.
  (In the future we should do some kind of bone-grouping or so)
- While transform(), the hotkeys G,R,S only switch mode when the previous
  mode was compatible. Caused conflicts with Crease/BoneDist/etc.
- Deleting the last VertexGroup now also deletes the entire Mesh 'dvert'
  data. Sounds logical, but remember that VertexGroups are partial on a
  Mesh, partial on Object. Weird design decision though...
  Anyhoo, at this moment the only way to have Bone Envelopes deform, is
  by deleting all VertexGroups!
- In PoseMode, the hotkey ALT+S now does both B-Bone size or Envelope,
  depending draw type.
- In EditMode, Extrude now also works when only Root points were selected.
- Weight editing is also symmetrical btw, with the "X-axis Mirror" option
  set.

source/blender/include/BIF_editarmature.h

@@ -43,7 +43,7 @@ typedef struct EditBone
 	struct EditBone *parent;/*	Editbones have a one-way link  (i.e. children refer
 									to parents.  This is converted to a two-way link for
 									normal bones when leaving editmode.	*/
-	void	*temp;		/*	Used to store temporary data */
+	void	*temp;			/*	Used to store temporary data */
 
 	char	name[32];
 	float	roll;			/*	Roll along axis.  We'll ultimately use the axis/angle method
@@ -59,17 +59,14 @@ typedef struct EditBone
 	int		flag;
 
 	int		parNr;		/* Used for retrieving values from the menu system */
-	/*	Storage for transformation data used by the posing system.
-		Maybe a better solution would be to make bones a blenderObject
-		variant?  Or perhaps to use a TOTALLY custom transformation scheme
-		for pose element, rather than trying to use the existing transObject
-		system?
-	*/
+	
 	float dist, weight;
 	float xwidth, length, zwidth;	/* put them in order! transform uses this as scale */
 	float ease1, ease2;
+	float rad_head, rad_tail;
 	short boneclass, segments;
-
+	
+	float oldlength;				/* for envelope scaling */
 
 } EditBone;
 
@@ -127,6 +124,10 @@ void armature_bone_rename(struct bArmature *arm, char *oldname, char *newname);
 void armature_flip_names(void);
 EditBone *armature_bone_get_mirrored(EditBone *ebo);
 
+void hide_selected_armature_bones(void);
+void hide_unselected_armature_bones(void);
+void show_all_armature_bones(void);
+
 #define	BONESEL_ROOT	0x10000000
 #define	BONESEL_TIP		0x20000000
 #define	BONESEL_BONE	0x40000000