allowing for resolved engines to be re-registered

[kdocki]

Currently if you want to override or decorate the blade compiler there doesn't seem to be a way. This is because once a engine is resolved it is used (so that we no longer have to keep making calls to resolve the registered engine). Imagine a service provider like below. The following will work after the merge but currently does not work)

      $app = $this->app;

        $resolver = $this->app['view']->getEngineResolver();

        $compiler = $resolver->resolve('blade')->getCompiler();

        $resolver->register('blade', function() use ($app, $compiler)
        {
            $extended = new ExtendedBladeCompiler($compiler);

            return new CompilerEngine($compiler, $app['files']);
        });

[taylorotwell]

Wrong branch. Would be a 5.0 change.