Shadowing warning between local variables or function depend on declaration order

Example:
```
contract C {
// no shadowing warning
function f() public pure { uint x; }
function x() public pure {}
}
```

```
contract C {
function x() public pure {}
// shadowing warning
function f() public pure { uint x; }
}
```

Discovered by @k06a

Reproduce both contract examples with the Solidity compiler and compare the shadowing warnings as declaration order changes. Trace the warning implementation from that behavior; done means the warning no longer depends on whether function x is declared before or after local variable x.

Written by the indexing model from the issue text.