New Squid messages missing translation

This is a patch against squid-2.5.STABLE10-20050603 that does the following:

- Translates errors/Spanish/ERR_INVALID_RESP to Spanish
- Replaces some ISO8859-1 characters by the preferred HTML code (i.e.
  "á" for "á").
- Minor typos or style fixes.
- Unifies the gender of "cache".
- Unifies the spelling of "cache" in spanish.

The last two changes deserve an explanation. The word "cache" in the
sense of a "web cache" or "cache memory" has not been formally (i.e. by
the "Real Academia de la Lengua Española" (Royal Academy of the Spanish
Language)) incorporated into spanish, therefore there isn't a sanctioned
spelling of the word. Nevertheless, the word is widely used in spanish,
but with inconsistencies: it is found both as a masculine and femenine
noun (spanish has only two genders, there is no neuter (it) pronoun) and
with at least two spellings. After a brief survey of the web, I set on a
single gender and spelling and fixed those error messages that were
using different ones (by virtue of being translated by different people).

-- 
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Juan Nicolás Ruiz         | Red de Datos de la Universidad de Los Andes
nicolas@ula.ve            | Edif. B (Fac. Ingeniería), Nivel Plaza
Telf. +58-(0)274-240-3889 | La Hechicera, Edo. Mérida, Venezuela
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