Support receiver parameter in method declaration

[TamasSzigeti]

What changed with this PR:

As it says on the tin

Example

    class Foo {
        public void bar(Foo this) {
            // noop
        }
        public void bar(Foo this, int y) {
            // noop
        }
    }

Relative issues or prs:

Fixes #607

[CLAassistant]

All committers have signed the CLA.

[jtkiesel]

This ended up being resolved by #642, so this PR can be closed.

[TamasSzigeti]

'pologies for the abandoned PR, thanks for fixing it elsewhere