What this changes:
* Before, a Version::GLES310 shader was created with `#version 450`
directive, which is wrong, because an implementation might support
GLES 3.1 but not GL 4.5 so this was not working and also the syntax
is a bit different so this wasn't helpful at all.
* Similarly, Context::isVersionSupported(Version::GLES310) was checking
for support of OpenGL 4.5. Now it just checks for
`ARB_ES3_1_compatibility` extension.
* Added a small isVersionES() utility that just tells whether given
version is ES or not.
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.
There will be many places (e.g. all
Platform::*Application::Configuration classes) where Version will be
used without Context (and all GL stuff brought with it).
SizeTraits class provides suitable types for given data size at compile
time, SizeBasedCall can call suitable templated overload based on given
data size at runtime.
Also added meta classes Pow and Log for computing powers and logarithms
at compile time, usable mainly in conjunction with SizeTraits. Their
implementation is checked at compile-time using static_cast().