YAML: correctly emit f as "!!bool false"
Temporary patch for dlists equality testing

Until https://github.com/slavapestov/factor/issues/1027 is resolved
Temporary patch for assoc-map on linked-assoc

Until https://github.com/slavapestov/factor/issues/1028 is resolved
YAML: cleanup, remove unreachable code
YAML: simple error when constructing undefined anchors
YAML: cleanup, don't prettyprint the linked-assoc

It's not useful because it's not homoiconic because of recursivity
YAML: handle recursive data and anchors' identity