Disconnects Store state fields from Compiler (#1761)

*  Moves CodeMemory, VMInterrupts and SignatureRegistry from Compiler
*  CompiledModule holds CodeMemory and GdbJitImageRegistration
*  Store keeps track of its JIT code
*  Makes "jit_int.rs" stuff Send+Sync
*  Adds the threads example.

crates/jit/src/link.rs

@@ -22,7 +22,7 @@ pub fn link_module(module: &Module, compilation: &Compilation) {
     for (i, function_relocs) in compilation.trampoline_relocations.iter() {
         for r in function_relocs.iter() {
             println!("tramopline relocation");
-            let body = compilation.trampolines[&i] as *const VMFunctionBody;
+            let body = compilation.trampolines[*i] as *const VMFunctionBody;
             apply_reloc(module, compilation, body, r);
         }
     }