[clang-tidy] Fix identifier naming for initializer list member initializers.

Summary:
This patch adds handling for member initializers in a constructors initializer list. Previously we only handled base-class and delegating initializers, which are transformed by the `TypeLoc` matcher. For Example:

```
// Style options: All identifiers should start with an upper case letter.
struct base { ...  }; 
struct der :  base {
  int field;  // FIXES: int Field;
  der() : der(42) {} // FIXES: Der() : Der(42) {}
  der(int X) : base(), field(X) {} // FIXES: Der(int X) : Base(), field(X)
  // Note that `field` doesn't get replaced
};
```

Reviewers: alexfh, hokein, aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D26744

llvm-svn: 287153