[wasmtime-api] Collect and wrap cranelift dependencies (#623)

* Collect and wrap cranelift dependencies
* rename all _cranelift_ named methods

crates/api/src/lib.rs

@@ -4,6 +4,7 @@
 
 mod callable;
 mod context;
+mod data_structures;
 mod externals;
 mod instance;
 mod module;