WASM import/export annotations

[kenchis]

For the old WASM backend it would be less error prone to have a default for the name in the Import and Export annotation.
Currently I have to repeat the method name.

Example (using method name processSamples):
@Import(module = ..., name = "processSamples") public static native void processSamples);
or (using the method name js2open)
@Export(name = "js2open") public static void js2open() { }
Proposal:
Let the method name be the default name, if name attribute is not specified:
@Import(module = ...) public static native void processSamplesJ);
and
@Export public static void js2open() { }
This proposal does not span the JSBody annotation for JS, where the method name occurs as well and since it contains arguments and such

[konsoletyper]

Yes, it's a good idea. However, legacy WebAssembly backend is of lowest priority for now.