Conf for doxygen based PHP doc

MediaWiki core is using Doxygen to generates it is documentation. It is
reasonably fast.

Provide a Doxyfile generated with version 1.8.8 with all comments and
default settings stripped out.

Assumes Graphviz is installed by setting HAVE_DOT = YES.

The documentation is generated by running doxygen at the root of this
repository, the doc is made available at docs/php/index.html

Bug: 72454
Change-Id: I3377a370bad65307968dd3f90433277daffebabb
ButtonInputWidget: Explicitly disallow setting value when using <input/>

There's weird interplay going on when we provide two setters for one
variable, and that's what we accidentally did.

Change-Id: I27221a27c00495a50d01144ac88921e83889801e
Merge "ButtonInputWidget: Explicitly disallow setting value when using <input/>"
Merge "Conf for doxygen based PHP doc"