[clang-tidy: modernize] Fix modernize-use-equals-default with {} brackets list...

[clang-tidy: modernize] Fix modernize-use-equals-default with {} brackets list initialization: patch

Summary:
Hello, i would like to suggest a fix for one of the checks in clang-tidy. 
The bug was reported in https://bugs.llvm.org/show_bug.cgi?id=38039 where you can find more information.

```
struct UOB{
	UOB(const UOB &Other):j{Other.j}{}
	int j;
};
```
In this case the check modernize-use-equals-default does not detect copy constructors that can be defaulted; that should be:

```
struct UOB{
	UOB(const UOB &Other) = default;
	int j;
};
```

Reviewers: aaron.ballman, hokein, alexfh

Reviewed By: aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D49356

llvm-svn: 337286