* Figured Bass: Break extender line if we have a different augmentation/diminished

So far, an extender line was only broken when a figure had a different alteration (+,-,!), but not if it had a different augmentation (\\, \+ or /). This patch also stores the state of the other modifiers and breaks the extender if they change.

[hanwenn, 2008-10-22 00:10:10]

LGTM - you might even want to see if you can fold repetitive code using a 

  SCM modifications[4]
  
and some loops

[Neil Puttock, 2008-10-22 20:48:15]

http://codereview.appspot.com/7644/diff/1/3
File lily/figured-bass-engraver.cc (right):

http://codereview.appspot.com/7644/diff/1/3#newcode105
Line 105: scm_gc_mark (groups_[i].alteration_);
Mark augmented_, diminished_ and augmented_slash_ too?