Three modules (ECMCoverageOption, ECMEnableSanitizers and
ECMGeneratePkgConfigFile) were not being documented. This commit fixes
that situation.

This is basically just the code available on the CMake FAQ item about
`make uninstall`, but packaged up in a convenient module.

REVIEW: 122359

This adds an application icon to an executable from PNG files for
Windows and Mac OS X. Unlike the similar kde4_add_app_icon macro from
kdelibs, this requires icons to be explicitly listed as arguments
(meaning CMake can tell when ones are added or deleted and reconfigure
as appropriate), and it works with Matthias Benkmann's png2ico tool, as
well as the KDE-Win tool of the same name.

Currently missing unit tests. Also completely untested (except that
`make test` runs on Linux, so there are no obvious syntax errors).

With thanks to Ralf Habacker for the inital work on porting
kde4_add_app_icon.

CHANGELOG: Add ECMAddAppIcon module to add icons to executable targets
on Windows and Mac OS X.

Add a couple of find modules for wayland-scanner and qtwaylandscanner.
These modules find the respective executables and create a target that
points to the executable.

Targets are respectively Wayland::Scanner and Wayland::QtScanner.

There are also macros to generate C protocols with wayland-scanner and
C++ wrappers with qtwaylandscanner.

REVIEW: 120034

add FindLibGit2.cmake + doc link
scripts tries to detect version not by pkgconfig to work on windows without pkgconfig, too
REVIEW: 120196

ecm_create_qm_from_po_files() was actually not very useful in practice.
So that is deprecated, to be removed before ECM 1.0.

Instead, the ECMPoQmTools provides several useful functions:
ecm_create_qm_loader() (which already existed in
ECMCreateQmFromPoFiles), ecm_process_po_files_as_qm() (which has the
same signature as gettext_process_po_files() from the FindGettext
module) and ecm_install_po_files_as_qm(), which is a convenience
function mostly for the benefit of KDE Frameworks (although potentially
useful for whatever other projects have the unusual requirement of a
Gettext translation workflow but no Gettext usage in the code).

NB: some clean-up to the documentation was done by Alex Merry
<alex.merry@kde.org> as part of this commit.

REVIEW: 117823

The ecm sphinx module occasionally tried to modify a list it was
iterating over, which is a Bad Thing and raised an exception on the
third or so time it was run without clearing the build directory.

REVIEW: 117780

ecm_dbus_add_activation_service() requires suffient knowledge of its
internals to use that replacing two lines with one seems silly.

In order to use it you have to know it behaves like configure_file()
(because you have to construct the file yourself), except that it also
installs it somewhere (for which you have to make sure
DBUS_SERVICES_INSTALL_DIR is defined before you use it, which is
certainly not a given for non-KDE projects). By this point, why not just
use configure_file() and install()? The DBUS_SERVICES_INSTALL_DIR
provided by KDEInstallDirs is all the magic you actually need, and if
that's explicit in the CMakeLists.txt file, it's a lot more obvious that
you should have it defined somewhere.

REVIEW: 117581