Because I got tired of having to manually postprocess ground truth files
for shader tests.
A bit strange / funny that the first ever version of my code manages to
produce smaller files than both stb_image and ImageMagick (with
-compress RunTimeLengthEncoded), for some reason both pick some strange
inefficient run combinations in various scenarios, such as "copy 2" +
"repeat 3" where I pick "repeat 5". And the difference is not
insignificant -- when testing with some shader test files, it resulted
in a ~17% smaller size!
The plugin follows the stricter variant of the spec by default (i.e.,
splitting runs across scanline boundaries) -- so that's *not* the
reason for the weird differences between my code and theirs -- but
provides an option to not do that for even smaller files. Which I'm
going to use for shader ground truth test files, because there every
byte counts. This option together with the above difference causes files
to be ~25% smaller, which is quite a lot.
Everything what was in src/ is now in src/Corrade, everything from
src/Plugins is now in src/MagnumPlugins, everything from external/ is in
src/MagnumExternal. Added new CMakeLists.txt file and updated the other
ones for the moves, no other change was made. If MAGNUM_BUILD_DEPRECATED
is set, everything compiles and installs like previously except for the
plugins, which are now in MagnumPlugins and not in Magnum/Plugins.