dont allow override color styles in elvis.syn

[fbrau]

allow a flag to "color ..." statements in elvis.syn
to not let elvis.clr change those colors

for example "color fixed ..." instead of "color ..."

Why?
Maybe I'm overstretching elvis coloring capabilities but this could favour
a style I'm using declaring some "starting" tokens in one color and "ending" tokens
in another one and elvis.clr not overriding this language customization

For example, the html files are colored like this:

keyword <div <span ...
color keyword on green
font operator </div </span ...
color operator on yellow

Even more, there could be some more extra font styles to favour this style, like
"font extra1", "font extra2", "font extra3".

So, the first enhancement should be "color [fixed]"
and the next enhancement should be allow more fonts font (extra1|extra2|extra3).

How invasive would be this?