Add a minimal SimpleJIT example program.

This minimally demonstrates usage of the API, and serves as a very small
testcase to test that the basic JIT mechanisms are working.

lib/simplejit/Cargo.toml

@@ -21,6 +21,9 @@ target-lexicon = { version = "0.0.3", default-features = false }
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = { version = "0.3", features = ["winbase", "memoryapi"] }
 
+[dev-dependencies]
+cranelift = { path = "../umbrella", version = "0.19.0", default-features = false }
+
 [features]
 default = ["std"]
 std = ["libc/use_std", "cranelift-codegen/std", "cranelift-module/std", "cranelift-native/std", "target-lexicon/std"]