[tex-eplain] Colors with hyperlinks

[Karl Berry]

    It also covers the \makeatletter, \makeatother and
    \resetatcatcode.  What I did was to have \makeat... define
    \resetatcatcode to restore the @ catcode.  Is this right?

Sounds good to me.

    +  \testfileexistence[miniltx]{tex}%

Would you mind writing up a paragraph or two and another example
documenting the optional arg to \testfileexistence?  (For the "Auxiliary
files" node, which seems like a poor choice of name on my part, but oh
well, can't fix everything.)

    +    \message{^^J\linenumber color.sty already loaded, refusing to reload it}%

Here's less drastic wording for this message:
\message{^^J\linenumber color.sty already loaded, skipping reload.}%

Thanks,
karl