Improve formatting of braced lists.

Before: vector<int> v{ -1};
After:  vector<int> v{-1};

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182597 91177308-0d34-0410-b5e6-96231b3b80d8
Increase test coverage for braced init lists.

Also fix a minor bug for constructor initializers with braced init lists.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182601 91177308-0d34-0410-b5e6-96231b3b80d8