bug#13409: [patch] make some error messages clearer

[Paul Eggert]

On 01/17/13 05:49, Pádraig Brady wrote:
> In fact it's very common to search for "error"
> in log files, which I do all the time looking
> for make errors in build logs.

Even when compiling error.c, verror.c, xstrtol-error.c, etc.?  :-)

I use Emacs's standard regular expressions to find errors like that,
and would find it annoying if every diagnostic had to have the
word "error" in it.  For one thing, these diagnostics typically
are not reporting errors (strictly speaking, an error is the
difference between an observed value and the theoretically
correct one).