Updated FindOpenGLES2.cmake from Magnum repository.
Fixed FindMagnumPlugins.cmake.

Didn't test it once. WTF.
Don't forward-declare struct as class.

Spotted by Clang.
Implicitly enable BUILD_STATIC also for Emscripten.
Uppdated and cleaned up development PKGBUILDs.
Added Emscripten PKGBUILD.
Updated toolchains submodule.