Add support for XMLConstants.ACCESS_EXTERNAL_DTD

[saurav1910]

For FEATURE_SECURE_PROCESSING support was added in #61
Getting Unrecognized property 'http://javax.xml.XMLConstants/property/accessExternalDTD'

java.lang.IllegalArgumentException: Unrecognized property 'http://javax.xml.XMLConstants/property/accessExternalDTD' at com.ctc.wstx.api.CommonConfig.reportUnknownProperty(CommonConfig.java:167) ~[woodstox-core-6.4.0.jar:6.4.0]

[gargvasu96]

Did You find any resolution for this issue? I am facing the same.

[cowtowncoder]

Not yet supported: if someone has time and interest, coming up with a patch might not be difficult -- just need to see exactly what are the semantics of this property and which of existing Woodstox config setting would work for it, if any.