Because even if it doesn't make a difference in practice, it is
technically more correct to call static methods statically. It
also better advertise that those methods can be used from any context.
Removed "unescape enclosure functionality", since the unescaping is already handled by fgetcsv,
and performing the unescaping again would actually result int the text from the cell being read wrong.
As an example try parsing the folowing CSV:
```
"<img alt="""" src=""http://example.com/image.jpg"" />"
```
With the additional unescaping it would have ended up as:
```
<img alt=" src="http://example.com/image.jpg" />
```
instead of the correct:
```
<img alt="" src="http://example.com/image.jpg" />
```
Fixes https://github.com/PHPOffice/PHPExcel/pull/1171
