The terminal now got a configurable palette for 16 colors (8 normal, 8
bright/bold).
<config>
<palette>
<color index="0" value="#000000"/> <!-- black is real black -->
<color index="8" value="#101010"/> <!-- bright black stands out a bit -->
</palette>
</config>
Note, the old (undocumented) <color index="..." bg="..."> configuration
scheme is no longer supported.
Also, this commit adds a pleasing default palette that ensures
readability of ViM's standard hightlighting.
Fixes#3406