3.1 Editorial improvements: non-step wrappers

[ndw]

Implementation experience has demonstrated that there are areas of the specification that didn't get the balance right between precision for implementers and clarity for users, for example “non-step wrappers”. The XProc 2.0 specification should attempt to resolve these problems without introducing inordinate complexity.

The 1.0 specification also defines the p:pipeline element as a syntactic shortcut for a particular form of p:declare-step. While convenient in some circumstances, it has proven to be a source of some confusion especially among new users. XProc 2.0 may remove the p:pipeline element.