Fix incorrect line breaking before trailing block comments.

Before, clang-format would happily move a trailing block comment to a
new line, which normally changes the perceived binding of that comment.

E.g., it would move:
void f() { /* comment */
  ...
}
to:
void f() {
  /* comment */
  ...
}

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183420 91177308-0d34-0410-b5e6-96231b3b80d8