[BUGFIX] Change explanatory text of SYS error reporting config variables

Unify explanatory text of the variables [SYS][errorHandlerErrors],
[SYS][exceptionalErrors], [SYS][syslogErrorReporting] and
[SYS][belogErrorReporting] so that formatting, link to PHP doc and
the numerical default values are similar.

Resolves: #61942
Releases: master, 6.2
Change-Id: Iacdbf18ad5c181c499c23c4c50cebffc6736236c
Reviewed-on: http://review.typo3.org/33025
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>