Extraneous space inserted after trailing comma

[bbannier]

In many places Zeek allows trailing commas. This seems to be handled inconsistently.

For enums I see expected behavior:

type E: enum { a, b, c, };

For set-like constructs I see an additional space:

const s = { 1, 2, 3,  };
#                    ^

const r: RecordType = [ $a=1, $b=2, $c=3,  ];
#                                         ^

We probably have the same issue for function-like constructors, e.g.,

const a = vector(1, 2, 3, );
#                        ^

The issue seems to be that we insert an space after , in the contexts even though it is not followed by more arguments.