Timers and modules

[davidgraeff]

This PR adds module support (not binary modules, just other files imported via the ES6 module syntax) and the js timer API (setTimeout, clearTimeout).

I wasn't really happy with bindings.rs being that one big huge file and refactored. This led to a big PR diff, but I'm willing to split this into smaller change-sets if the overall structure is something that this project want to go forward with.

The changes in detail. First commit:

• Patch makefile in build.rs to allow for cross compiling.
• Add quickjs-libc.h to wrapper.h and regenerate bindings.rs for module support.
• just: Let bindgen generate to src/bindings.rs
• Use src/bindings.rs directly in lib.rs instead of including a file from OUT (faster compile time!)

Second commit:

1. The bindings.rs file grew to one huge file with many different aspects covered. It is now split into value/marshal for ser/deserializing of JsValues and owned_value_ref for the OwnedValueRef type and utils for general utility methods.

2. DroppableValue was used in two ways: Either as a OwnedValueRef with a context pointer (instead of a ContextWrapper like OwnedValueRef uses it) or for the Properties enumeration. DroppableValue has been completely removed instead and OwnedValueRef takes a context pointer now. For properties enumeration a new type has been introduced (see value/marshal.rs).

3. impl ContextWrapper has been split into multiple impl ContextWrapper's, so that the callback API, timer API, module support each stay in their own rust-modules. bindings.rs is now purely for state keeping and the eval related API with about 500 LOC instead of 2k LOC.

4. Compiling to bytecode and running from bytecode has been added.

5. The timer API setTimeout/clearTimeout has been added. resolve_value required a few changes to "wait" for all timers to expire before returning.

6. Allow callback function arguments for add_callback and create_callback APIs. A new OpaqueJsFunction type (a simple-type wrapper around OwnedValueRef) is introduced for this. Usage example:

fn register_state_listener(id: String, callback_function: OpaqueJsFunction) -> i32 {
    let _ = callback_function.invoke(vec![id]);
    0

}
context.add_callback("notifyOnStateChange", register_state_listener)?;

7. Allow for a "generic" function argument for add_callback and create_callback APIs. This is useful if a js-api consumer is allowed to hand in a number, a string, a boolean. Usage example:

fn set_named_output(var_name: String, var_value: JsSimpleArgumentValue) -> JsValue {
    println!("setNamedOutputValue {} {:?}", var_name, var_value);
    JsValue::Null
}

[theduke]

Hey sorry for the delay, I'll get to it this weekend.