Fix display of MusicPunctuation (again)

[annplaksin]

I broke the display of MusicPunctuation with my latest change of drawing linebreaks in TextUnderlay. Especially when a space follows it gets bad...

<treatise>
Fix MusicPunctuation again...

<example: {full measure}, {mensural: void}, {staf: "5" BU Br1 Per1 Per2 Bo2 : "6" V, red}> 
<part: 2><label: rot90c, 12><red>Tenor</red></label> {clef: "C10" V BU : "C8" Br1 Per1 Per2 Bo2} {solm: 0} {mens: C7} 
{prop: 2/1, 7-9} <label>{var=(ins.) "Dupla do semi. per batt." Per2}</label> Lc<text>sta{.,} Via</text>. {var=(ins.) "{staf: 5} {clef: C10} {solm: 0}" Br1 : "<lig>SG Sa</lig> <lig>Sb Sc</lig>" Bo2^* : (struck through) Bo2^c} <lig>Sa Sb</lig> <lig>Sc Sd</lig> {var="SG" V BU Br1 Per2 Bo2^c : "mG" Bo2^*} <text>rege nos in ista{.,}</text> Pm5 mF {var="<lig><obl>Sb Sa</obl> Ld</lig>" V BU Br1 Bo2 : "<lig>Sb Sa</lig> Ld" Per2} Bc <lig><obl>Bb Ba</obl></lig> {mens: C5} BG Pm9 Sc <text>Ut te recto-</text> mb ma {var=(ins.) "{staf: 6} {clef: C8} {solm: 0}" V} Sd mc {var=(ins.) "{staf: 5} {clef: C8} {solm: 0}" Br1} ma mc Sb {prop: 4/1, 5-7} <label>{var=(ins.) "Quatrupla quattro semi. per bat." Per2}</label> Ma <text>re{ ,}</text> </part>
</example>
</treatise>