Don't remove blank lines within unwrapped lines.

If the code author decides to put empty lines anywhere into the code we
should treat them equally, i.e. reduce them to the configured
MaxEmptyLinesToKeep.

With this change, we e.g. keep the newline in:
SomeType ST = {
  // First value
  a,

  // Second value
  b
};

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175620 91177308-0d34-0410-b5e6-96231b3b80d8