Require path separators in assignments/overrides

Require path separators in assignments/overrides

Historical assignments/overrides like
Variable #'x #'y = 7
or
\override Glissando.bound-details #'left #'Y = #3
without dots between the various path components do not match the syntax of
\revert and music functions or other uses.  Disallow the non-separation
by '.' or ',' of such path components.

[thomasmorley651, 2016-03-13 23:28:34]

Can't review parser-code, but from description:
This is the logical consequence of your previous work.
I vote for it.
Offtopic: time for v2.20 ?

[lemzwerg, 2016-03-14 06:40:27]

LGTM.

I assume that convert-ly already does the right thing...

[dak, 2016-03-14 07:06:11]

On 2016/03/14 06:40:27, lemzwerg wrote:
> LGTM.
> 
> I assume that convert-ly already does the right thing...

Somewhere in the leadup to 2.18.  However, i kept \override Context.Grob
property.subproperty (without the dot in the middle) working.  It's just the
subproperty subdivision dot that is no longer optional.

[dak, 2016-03-14 21:12:04]

Fixed the oversight in the snippets.  Hopefully the only one.