* Don't set $IP. The entry point already sets it, so there's no point. Users can still set it if they can figure out a way to do it without breaking things.
* Don't include DefaultSettings.php. Doing that is code, not configuration, and it can easily be done in WebStart/Maintenance. Some non-standard entry points in extensions may be broken by this. That's their fault for being non-standard. Backwards compatibility is preserved thanks to require_once().
* Introduce $wgInvalidateCacheOnLocalSettingsChange, which when set, causes $wgCacheEpoch to be updated in the way that it previously was in the default LocalSettings.php.
* Don't set $wgLocalInterwiki to some nonsense value (possibly including spaces and punctuation in the new installer). It should be only for actual interwiki prefixes. Since most wikis don't have them, I set this to false by default and adjusted the referring code to accept this.
* Removed the guard for web invocation with $wgCommandLineMode set. This ancient code is redundant with modern protections in doMaintenance.php.
* In DefaultSettings.php, fixed fold terminator placement near $wgLoadScript
* Add a web entry point guard. That's one piece of code which really is necessary.
Updated all nextSequenceValue calls with new sequence names.
OverlordQ stated he'll handle changes to Postgres scripts.
Need someone to change DB2 scripts.
As Tim notes, the weird callback setup in $wgHooks isn't really something we want to replicate or ever rely on ever again, as PHP's native callback syntax already handles things fine and is more consistent (and used extensively in the rest of MediaWiki).
May be other remaining issues with the refactor on top of bugs already discovered, but if it's going to be refactored to use callbacks it should be done using regular callbacks.
This doesn't work as intended; when editing existing articles, this'll pull the *previous* redirection state of the article, rather than the current state, so it's wrong whenever a page is changed into, or away from, being a redirect.
NOTE: Wikimedia's secure.php needs to be updated to use the new variable. It might be possible to retire the fixupSquidUrl() hack once this is done, though I'm not sure if anything else relies on it.
Also simplify URL construction: old code used to call Title::getInternalURL() to build the URLs and then undo most of the work with preg_replace().
(TODO: Maybe consider introducing new global $wgIRCLineURLPrefix to optionally override the $wgInternalServer.$wgScript prefix?)
