Create \temporary for doing overrides without pop-first set (issue 6687044)

[janek . lilypond]

Hi,

from what i understand, the current situation is:
1) we'd like to see the interface for changing properties redesigned
(http://lists.gnu.org/archive/html/lilypond-devel/2012-10/msg00518.html),
2) the above won't happen sooner than several months from now,
3) we are not sure whether we want to have \temporary or maybe change
\override itself to be just push,
4) anyway, we need to change current behavior because it's buggy.

So, i suggest to wait for that discussion to end (i could use more
replies to
http://lists.gnu.org/archive/html/lilypond-devel/2012-10/msg00519.html).

But the patch itself, shall we choose to use \temporary, LGTM.


http://codereview.appspot.com/6687044/diff/4001/ly/music-functions-init.ly
File ly/music-functions-init.ly (right):

http://codereview.appspot.com/6687044/diff/4001/ly/music-functions-init.ly#newcode1250
ly/music-functions-init.ly:1250: @emph{corresponding} reverts in a
stack-neutral manner.  An
Could you write explicitely both here and in the commit message that "as
of 2.17.5, \override is a pop+push"?

Had i not participated in previous discussion, i would have no idea why
some overrides could be pop-first and what that could actually mean to
the music.

http://codereview.appspot.com/6687044/