CSS classes starting with special characters (Umlaut, accent, cyrillic, greek) are ignored (1.0.x)
#### Steps to reproduce:
- open [T43422___14S55o554S.svg](/uploads/212992e0f44977eefd818e16da0df9d9/T43422___14S55o554S.svg)
```xml
<?xml version="1.0" encoding="UTF-8"?>
<svg width="464px" height="528px" version="1.1" viewBox="-2 -2 464 528" xmlns="http://www.w3.org/2000/svg">
<style type="text/css">
rect.группировка{stroke-width:4;stroke-dasharray:10,10}
.стрелка{marker-end:url(#a);stroke-width:4}
</style>
<defs>
<marker id="a" markerHeight="6" markerWidth="7" orient="auto" refX="7" refY="3" viewBox="0 0 7 6">
<path d="m7 3-7-3q2 3 0 6z"/>
</marker>
</defs>
<rect class="группировка" width="460" height="240" fill="none" stroke="#000"/>
<line class="стрелка" x1="220" x2="220" y1="300" y2="340" stroke="#000"/>
</svg>
```
#### What happened?
#### What should have happened?
- the rect should be `rect.группировка{stroke-width:4;stroke-dasharray:10,10}`
- the line have a marker-end `.стрелка{marker-end:url(#a);stroke-width:4}`
#### Inkscape Version and Operating System:
- Inkscape Version: Inkscape 0.92.4 5da689c313, 2019-01-14
- Operating System: Ubunut 18.04
#### Source
https://commons.wikimedia.org/wiki/File:T43422_%D0%A1%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0_%D1%83%D0%BF%D1%80%D0%B0%D0%B2%D0%BB%D0%B5%D0%BD%D0%B8%D1%8F_%D0%9A%D0%90.svg
issue