m_operprefix Don't set +y on the oper if hideoper is being unset due to deopering

Fixes issue #801 reported by @UselessOper
m_httpd Fix typo noticed by @SaberUK
m_globalload Don't pass a callback to ModuleManager::Reload() if reloading m_globalload
m_watch Validate targ before use, noticed while rewriting m_watch for 2.2
Major example configuration and helpop update

Big thanks to @m4z (#621) and @Robby- (#630) who contributed a lot to this
Fix typos and update text in the configure script

Some of these were picked from #448
Add REG_ALL checks to treat unregistered users as nonexistent in more cases
Fix snotice about disabled command usage being sent to the wrong snomask