Remove synchronous compilation/enhanced-require support #84
Description
We should remove the synchronous path from the less-loader. It makes the code a lot harder to understand and impairs contribution. enhanced-require is now unmaintained for 2 years and @sokra is recommending to use target: "node" in order to prepare your bundle for the server-side.
Additionally synchronous compilation is really inefficient and may slow down the application bootstrap significantly.
I've added a deprecation warning to the code so people have the chance to give us feedback. Maybe there's a use-case we haven't seen yet.