Remove the trimming operation on LabelString, LabelStringAppendix,
EndLabelString and LabelCounter. This trimming meant that quotes
strings were not preserved, which is wrong.
To preserve layouts, the Layout format has been updated to 64, so that
layout2layout can remove extra spaces on existing strings, which
ensures that behavior is unchanged for old layouts (courtesy of rgheck).
It is now possible to re-add spaces in label strings where it makes
sense.
Fixes bug #10723.
In June the R-SS phrase system is replaced officially by the GHS H-P statement system in the EU.
So just in time here is support for this.
No new LaTeX package is required since the already supported package mhchem provides the statements.
