Formalize $schema inheritance/cascade/whatever

Author: handrews

jsonschema-core.xml

@@ -1175,7 +1175,8 @@
                     <t>
                         If multiple schema resources are present in a single document, then
                         schema resources which do not have a "$schema" keyword in their root
-                        schema object inherit the meta-schema from the enclosing resource.
+                        schema object MUST be processed as if "$schema" were present with the
+                        same value as for the immediately enclosing resource.
                     </t>
                     <t>
                         Embedded schema resources MAY specify different "$schema" values from their