This version of wasmer improves significantly the Emscripten backend making it compatible with the latest Emscripten LLVM release. It also improves the dependency graph between modules and improves the caching strategies.

Changelog

• #541 Fix dependency graph by making separate test crates; ABI implementations should not depend on compilers. Add Cranelift fork as git submodule of clif-backend
• #537 Add hidden flag (--cache-key) to use prehashed key into the compiled wasm cache and change compiler backend-specific caching to use directories
• #536 Update cache to use compiler backend name in cache key