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/runtime/Cargo.toml

@@ -21,6 +21,7 @@ thiserror = "1.0.4"
 more-asserts = "0.2.1"
 cfg-if = "0.1.9"
 backtrace = "0.3.42"
+lazy_static = "1.3.0"
 
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = { version = "0.3.7", features = ["winbase", "memoryapi", "errhandlingapi"] }