fix Issue 10326 - Disallow 'invariant' for immutable, allow class/struct invariants without (), and later disallow usage of ()
Replace 'invariant' to 'immutable' in comments
Merge pull request #3540 from 9rnsr/fix10326

Issue 10326 - Disallow 'invariant' for immutable, allow class/struct invariants without (), and later disallow usage of ()