A terminating line break has not been required in wfDebug() since 2014,
however no migration was done. Some of these line breaks found their way
into LoggerInterface::debug() calls, where they mess up the formatting
of the debug log.
So, remove terminating line breaks from wfDebug() and
LoggerInterface::debug() calls.
Also:
* Fix the stripping of leading line breaks from the log header emitted
by Setup.php. This feature, accidentally broken in 2014, allows
requests to be distinguished in the log file.
* Avoid using the global variable $self.
* Move the logging of the client IP back to Setup.php. It was moved to
WebRequest in the hopes that it would not always be needed, however
$wgRequest->getIP() is now called unconditionally a few lines up in
Setup.php. This means that it is put in its proper place after the
"start request" message.
* Wrap the log header code in a closure so that variables like $name do
not leak into global scope.
* In Linker.php, remove a few instances of an unnecessary second
parameter to wfDebug().
Change-Id: I96651d3044a95b9d210b51cb8368edc76bebbb9e
