Doc updates from NEWS

[Graham Percival]

Cameron, you can delete
2.8
"Subproperties, like the details field of Slur and Tie may now be tuned 
with \override. [This obviously belongs in Section 9, but I don't 
understand it enough to say more!]"
(I've documented that)
Full list at   http://web.netcall.com.au/horsburgh/DocUpdate.html



Everybody else, do any of the below items need to be in the docs?  If 
so, please write something for them, because I don't understand them.  
This is the last call; if nobody writes something for these soon, we'll 
remove them from the TODO list.  (Actually, even if somebody _does_ 
write docs for them, they'll still be removed from the list.  :)

# Each grob property may also be a "grob closure." This means that it 
is possible to combine functions.
#

# Generic music functions may now also be used on articulations and 
chord elements
#

# String arguments for music functions may be specified without # 
marks. Now, \clef and \bar are also music functions.
#

# Calculation of extent and offset of grob is now controlled via the 
X-extent, Y-extent, X-offset and Y-offset properties, [I suspect this 
is documented, but I don't really understand it enough to tell for 
sure.]
#

# Each grob property can be a procedure. If this is the case, it is 
assumed to be a routine that calculates said property. This is a major 
internal cleanup, which also provides advanced tweakability for power 
users. [I don't even know what this means...!]