changed <dom> and <input> parser such that the following conditions actually work:

changed <dom> and <input> parser such that the following conditions actually work:
1) no <input> element at all
2) empty <input> element
3) <input> element starting with an <xslt> instruction (that is, <xmlreader> and/or <marc> not mandatory any more.
Needed to make new define DOM_INPUT_DOM besides DOM_INPUT_MARC and DOM_INPUT_XMLREADER
Still missing detection of <xmlreader> or <marc> after all <xslt> nodes.
And more important: when finding errors here, it's kind of lam just to emit an warning, one should stop processing!