multi-line scalar doc starting on header is not supported
test coverage for quotes in quotes
fix xt comparison tests

Implemented new cross-parser YAML->Perl comparison test against
all t/tml-local/yaml-roundtrip and t/tml-world TestML files.

Removed xt/compare/04_scalar.t as it was redundant.
use own cmp_deeply instead of is_deeply

cmp_deeply provides better diagnostics