highlight named parameters in FB/function calls

[michaeldistel]

Summary

Named parameters in FB and function calls (IEC 61131-3 §2.5.1) are not highlighted distinctly. The parameter name before := should be scoped separately from regular identifiers.

Example

MyTimer(IN := StartSignal, PT := T#5s);
Result := MyFunc(Input1 := Val1, Input2 := Val2);

IN, PT, Input1, Input2 should be scoped as variable.parameter.st.

Acceptance criteria

• Parameter names before := in call expressions scoped as variable.parameter.st
• Does not affect regular assignment statements
• Does not affect output parameter assignments (=>)