#42 VSFilter 2.27: USF issues

[Kovács Endre János]

- Nested elements will render incorrectly after around 3
levels.
Example:
<text style="mewmew end Pink1"><font
color="#D79A57">So<font
color="#06AA13">me</font></font>thi<font
color="#005EBB">ng </font>swe<font
color="#D79A57">et <font color="#005EBB">and <font
color="#06AA13">so<font color="#A07BBF">ur
</font></font>wo</font></font>uld <font
color="#06AA13">be </font>good <font
color="#06AA13">too <font color="#005EBB">!
</font></font></text>

- Named entities <, > and & are not parsed
(these are the only named entities used in unicode xml,
so this one should be pretty easy to fix)

The following are missing features which could be
implemented by simply mapping the appropriate
attributes to their STS equivalent:

- The alpha element is ignored in USF color codes
- rotate-x, rotate-y and rotate-z are ignored