Allow local interwiki links with an empty title part

For example, [[en:]] on enwiki. These links were for some reason considered
invalid. However, to support use-cases such as cross-wiki transclusion and
the importing of templates across wikis, this type of link should be
allowed.

I can't see that this would break anything. If anything, it will "un-break"
some links.

Should MediaWikiTitleCodec depend on Title::newMainPage? Almost certainly
not, but I note that splitTitleString is earmarked for demolition, so I
expect that the confusing dependency-web will be cleaned up in the future.
I also note that MediaWikiTitleCode already uses various static methods of
the Title class.

Bug: 64167
Change-Id: I27495aa62e6059c7725387135ae0358d7e6fb35b
Porting file test from browsertests

Testing in bare wiki, beta enwiki and hewiki

Change-Id: If8262a7798c19dad84f9ceb88a5e286a90cf2a39
QA: porting login test from /qa/browsertests

Tested in local bare wiki, beta hewiki and enwiki

Change-Id: Icf060de7697cb43d9a8d28c036d4efcbdfd64720
QA: updates to edit test ported from qa/browsertests

Change-Id: I2ceae6ee6f98df78c12d257fd6503f5bf6395284
SpecialSearch: Fix overlap between results info and search bar

Followup to 1896d06, lost a clear:both in the process.

Bug: 67184
Change-Id: If0b6df347315bfe5b6f9a7aa9c6730cbdf44fd38
Add ids to the old link and the new link at the move result

This is immediately useful for building a GuidedTour
for moving a page, and can be useful for other things as well.

Change-Id: I2765248f61ecd3089a9f4e06571a378e39ec1db3
Merge "QA: porting login test from /qa/browsertests"
Merge "QA: updates to edit test ported from qa/browsertests"
Merge "Porting file test from browsertests"
HTMLForm submission callback documentation updates

The possibilities for the submission callback return value were
documented in three different places, and none were entirely correct.
Related documentation could also use a cleanup.

Change-Id: Ib3621a0d5ba24c481f3117b547bca70d4ca50ba2
Merge "SpecialSearch: Fix overlap between results info and search bar"
Merge "Add ids to the old link and the new link at the move result"
Merge "Allow local interwiki links with an empty title part"
Merge "HTMLForm submission callback documentation updates"
Localisation updates from https://translatewiki.net.

Change-Id: I19bae9c3074a69f36a12636ce23434681d763c7c
Use some callable hints on @param docs

Callbacks can be given as a string or array, so the hint 'callable' is
used.

Change-Id: I3842606f74c8c3705dffc70bf13e31f44a37fa65
Fixed broken exception code

Change-Id: Id399cb22f183d75acc006e698feb161bd12096bd
Merge "Use some callable hints on @param docs"
Merge "Fixed broken exception code"
Don't link to PHP @ php.net when running HHVM

Change-Id: Ifdec12e093fdd29d76ccb4b9e3ec58a6bceb47ed