[Sync-En] faq: fix typos and grammar

[lacatoire]

Translation of php/doc-en#5898 (commit 7ab5409): the faq pages mirror the upstream wording fixes, the para to simpara conversions, and the renamed faq.general.running-concurrent and faq.passwords.storing-salts ids. EN-Revision updated.

Fixed a number of defects in the same files along the way: sentences that said the opposite of the original (cp *.o functions, the GET urlencode note, the make Si no lo hace hint), garbled or untranslated passages, a tutoiement, matriz for arrays and librería/bandera against the glossary, and spelling and accent errors.

Fixes: #1376