Remove Module's finalize_function and finalize_data. (#519)

* Remove `Module`'s `finalize_function` and `finalize_data`.

Remove the ability to finalize individiual functions and data objects,
and instead just provide a way to finalize everything that's been
defined but not yet finalized. This allows SimpleJIT to share an
allocation between multiple functions without having to worry about
individual functions being finalized and needing to be published
without the other functions in the same allocation.

Users of the return values of `Module`'s `finalize_function` and
`finalize_data` should now use `get_finalized_function` and
`get_finalized_data` to obtain these values.

lib/simplejit/tests/basic.rs

@@ -57,13 +57,15 @@ fn define_simple_function(module: &mut Module<SimpleJITBackend>) -> FuncId {
 }
 
 #[test]
-#[should_panic(expected = "function can't be finalized twice")]
-fn panic_on_double_finalize() {
+fn double_finalize() {
     let mut module: Module<SimpleJITBackend> = Module::new(SimpleJITBuilder::new());
 
     let func_id = define_simple_function(&mut module);
-    module.finalize_function(func_id);
-    module.finalize_function(func_id);
+    module.finalize_definitions();
+
+    // Calling `finalize_definitions` a second time without any new definitions
+    // should have no effect.
+    module.finalize_definitions();
 }
 
 #[test]
@@ -72,6 +74,6 @@ fn panic_on_define_after_finalize() {
     let mut module: Module<SimpleJITBackend> = Module::new(SimpleJITBuilder::new());
 
     let func_id = define_simple_function(&mut module);
-    module.finalize_function(func_id);
+    module.finalize_definitions();
     define_simple_function(&mut module);
 }