bug#13369: 24.1; compile message parsing slow because of omake hack

[Glenn Morris]

Mattias Engdegård wrote:

> 8 jan 2013 kl. 21.14 skrev Glenn Morris:
>
>> Thanks. Could you also give the numbers for
>> compilation-error-regexp-alist containing only `gnu' (assuming that is
>> the one that is relevant for your test case)?
>
> These times are with a slightly different compilation buffer:
>
>   all   no omake   gnu only
>  32.7     3.4        0.3      standard code
>   6.8     3.4        0.3      repaired regexp (escaped ^)
>   3.4     3.4        0.3      COND expression removed

OK, thank you. So having fixed the omake ^ issue, basically to me it
just seems to be the case that the more entries are in
compilation-error-regexp-alist, the slower things get.

Maybe we should encourage people to prune it to only the entries they
use, or maybe some less common elements should not be there by default.