Allow breaking before a trailing const.

Before:
void someLongFunction(
    int someLongParameter) const;

After:
void someLongFunction(int someLongParameter)
    const;

Also slightly cleanup tests.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@182362 91177308-0d34-0410-b5e6-96231b3b80d8