Issue deprecation warning for pre-2.18 override syntax
Old override (and revert) syntax was
\override Stem #'transparent = ##t
or
\override Voice.Stem #'transparent = ##t
This deprecated syntax is now flagged with a warning. Property paths used as music function arguments do not work without that dot, and the inconsistency is not helpful.
This will mostly affect source code not passed through convert-ly
since the conversion patterns catch (most?) uses.