[jsx] Use write_varref() for groupings
[jsx] Use write_varref() for groupings

The code was using write_varname() prefixed with "~n.", but that's
conceptually wrong - fix write_varref() to work as it should and
use that.

snowballstem/snowball,snowballstem/snowball,snowballstem/snowball,snowballstem/snowball,snowballstem/snowball,snowballstem/snowball,snowballstem/snowball,snowballstem/snowball