Adds files: error 1 to 5 and variation 1 to 4
tests for error1: not well formed xml
tests for error2: not well formed xml attribute without colon
tests for error2: not well formed xml, typo
tests for error4: wrong xml version
tests for error5: extra content at the end of the doc
tests libxml_dtd_load
tests libxml_dtd_valid
tests for libdtd_noerror
tests for LIBXML_DTDATTR, LIBXML_NOCDATA, LIBXML_NOENT and LIBXML_NOBLANKS
the basic behavior
fix comments