Improve support for legacy ast

[montyly]

From Solidity 0.6.3 to 0.6.10 (included) the comment above events and functions are added to the children of the event/signature in the legacy Ast.

Example:

contract A{
    /*** Events ***/
    event E();

    /*** Function ***/
    function f() public{}
}

======= test.sol =======
{
  "attributes":
  {
    "absolutePath": "test.sol",
    "exportedSymbols":
    {
      "A":
      [
        9
      ]
    }
  },
  "children":
  [
    {
      "attributes":
      {
        "abstract": false,
        "baseContracts":
        [
          null
        ],
        "contractDependencies":
        [
          null
        ],
        "contractKind": "contract",
        "documentation": null,
        "fullyImplemented": true,
        "linearizedBaseContracts":
        [
          9
        ],
        "name": "A",
        "scope": 10
      },
      "children":
      [
        {
          "attributes":
          {
            "anonymous": false,
            "name": "E"
          },
          "children":
          [
            {
              "attributes":
              {
                "text": "* Events **"
              },
              "id": 1,
              "name": "StructuredDocumentation",
              "src": "16:16:0"
            },
            {
              "attributes":
              {
                "parameters":
                [
                  null
                ]
              },
              "children": [],
              "id": 2,
              "name": "ParameterList",
              "src": "44:2:0"
            }
          ],
          "id": 3,
          "name": "EventDefinition",
          "src": "37:10:0"
        },
        {
          "attributes":
          {
            "functionSelector": "26121ff0",
            "implemented": true,
            "isConstructor": false,
            "kind": "function",
            "modifiers":
            [
              null
            ],
            "name": "f",
            "overrides": null,
            "scope": 9,
            "stateMutability": "nonpayable",
            "virtual": false,
            "visibility": "public"
          },
          "children":
          [
            {
              "attributes":
              {
                "text": "* Function **"
              },
              "id": 4,
              "name": "StructuredDocumentation",
              "src": "53:18:0"
            },
            {
              "attributes":
              {
                "parameters":
                [
                  null
                ]
              },
              "children": [],
              "id": 5,
              "name": "ParameterList",
              "src": "86:2:0"
            },
            {
              "attributes":
              {
                "parameters":
                [
                  null
                ]
              },
              "children": [],
              "id": 6,
              "name": "ParameterList",
              "src": "95:0:0"
            },
            {
              "attributes":
              {
                "statements":
                [
                  null
                ]
              },
              "children": [],
              "id": 7,
              "name": "Block",
              "src": "95:2:0"
            }
          ],
          "id": 8,
          "name": "FunctionDefinition",
          "src": "76:21:0"
        }
      ],
      "id": 9,
      "name": "ContractDefinition",
      "src": "0:99:0"
    }
  ],
  "id": 10,
  "name": "SourceUnit",
  "src": "0:100:0"
}