Support for dangling commas

My comrades, I beg of you, please support dangling commas. It reduces AST diff churn, it makes sense. Search your hearts you know its the right thing to do.

I pray for your good health,

Cheers

The issue names no files, tests, or parser entry points. Start by locating where Solidity syntax is parsed in this experimental Haskell compiler, then determine the affected grammar cases and how parser tests are organized. Done means dangling commas are accepted consistently and covered by tests without changing unrelated syntax.

Written by the indexing model from the issue text.