#145748 by meba, after coding style fixes: disable the checkbox on the default language, so it cannot be disabled (the submit handler already disallows disabling it)

as a side effect, improve usability of the module screen by performing module
changes all at once

- Patch #144859 by dww: added optional e-mail notifications when user are approved, blocked, or deleted.

- Patch #105039 by ChrisKennedy: more polish for the custom date formats. Previous custom data format patch was also by Chris but got accidentically committed with another patch.  Thanks Chris.

#143249 by Jose A Reyero: add language parameter to t() to make it possible to retrieve translations of strings for different languages, to send emails to users in their own language for example

#141637 follow up patch by merlinofchaos: proper placement of menu_rebuild() to not run twice on the same request

#136837 by meba: PHP replaces {} enclosed variables in strings with the variable value itself, so cache tables were not prefixable