Make music functions and identifiers and expressions take articulations

Make music functions and identifiers and expressions take articulations

Since the resulting mess would be too large when doing this in music
function arguments and similar locations, for now this is possible only
inside of chords and inside of music sequences.

[lemzwerg, 2014-03-21 08:27:41]

LGTM.  Does this change deserve a regtest?

[dak, 2014-03-21 08:40:26]

On 2014/03/21 08:27:41, lemzwerg wrote:
> LGTM.  Does this change deserve a regtest?

It deserves several regtests, change entry, documentation, and probably
additional work to cover more cases.  There are LSR examples and Scheme
programming examples based on the premise that you cannot add articulations in
LilyPond once a music expression has left the parser.

Doing this thoroughly is a lot more work.  Still, this change should in the
current form hopefully not affect currently valid programs: at least it did not
require additional precedence rules and did not cause reduce/reduce conflicts. 
That's not a full guarantee (if there are new conflicts, existing precedence
rules might suffice to resolve them, but with changed results).  But if this
passes regtests, it is at least encouraging.

[thomasmorley651, 2014-03-21 10:13:17]

Can't review parser code.
From description: great