It doesn't really work for tests that depend on more than one plugin
(because there i would need to handle all combinations, somehow), but it
does the job when the end user has such use case.
Moreover, doing them here would mean the options might get ignored with
no clear reason why. Aaand yes of course this caused MagnumFontConverter
to be skipped for no clear reason on embedded platforms, and uncovered a
setup bug in the test.
Added new root CMakeLists.txt file, the old include paths are used only
if MAGNUM_BUILD_DEPRECATED is set, thus it can now compile and install
only if deprecated build is enabled.
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.
Moved them to `OpenGL/` subdirectory, allowing them to be included
explicitly with e.g. <OpenGL/GLES2/gl2ext.h> overriding the system
<GLES2/gl2ext.h> header. Our versions of the headers are thus now
explicitly included in `OpenGL.h`, but they can be also included using
no-prefix path if no system version is available. It might break some ES
platforms, they will be fixed when found.
The headers are now installed into `Magnum/OpenGL` (not into any
artificial `external` directory). Now also installing GLES2 headers for
OpenGL ES 2 (previously ES3 headers were installed for both ES2 and
ES3).