YAML::Literal when new line at the end, shoud be `|+` and not `|`

[shemeshg]

it is ok for

YAML::Emitter out;
out << YAML::Literal << "A\n B\n  C";

to produce

|
A
 B
  C

But

YAML::Emitter out;
out << YAML::Literal << "A\n B\n  C\n";

should have produced

|+
A
 B
  C