A zero-indent literal or folded block scalar sits at column 0, where the
directive scan runs, so a content line beginning with `%` (`%!PS-Adobe-2.0`)
was misread as a directive and rejected as unsupported.
The directive scan now runs only outside a block scalar, so a leading `%` in
block scalar content is literal text. A real `%YAML` or `%TAG` directive still
parses, and a stray `%` in other content is still rejected rather than silently
accepted, so the should-error behaviour is unchanged.
This is groundwork for yaml-test-suite W4TN, which additionally needs a block
scalar to be terminated by `...` and per-document directives across a multi-
document stream, so conformance counts are unchanged this step.
Mihaela M
942a7ff2bc