Small errors in xproc.rng: some attributes are actually mandatory

[GerbenAbbink]

We are using xproc10.rng and xproc30.rng for code completion and we have found an error: All attributes that are "required" in the XProc standard are optional in the relax schema. For instance:

Here "attribute-name" is "required": https://spec.xproc.org/master/head/steps/#c.add-attribute

Here "attribute-name" is "optional": https://spec.xproc.org/master/head/xproc/xproc30.rng

We have found so far: add-attribute @attribute-name add-attribute @attribute-value add-attribute @match delete @match directory-list @path error @code filter @select wrap @match wrap @wrapper xsl-formatter @href

[ndw]

Unfortunately, it's not possible to make the option shortcut forms mandatory because, this has to be allowed:

<p:add-attribute>
  <p:with-option name="attribute-name" select="/doc/name">
    <p:pipe ...>
  ...
</p:add-attribute>