use xmlSchemaSetValidStructuredErrors ...
use xmlSchemaSetValidStructuredErrors ...

... to explicitly print out the filename, line number and error message

fixes #135

melven/tixi,DLR-SC/tixi,melven/tixi,DLR-SC/tixi,melven/tixi,melven/tixi,melven/tixi,DLR-SC/tixi,DLR-SC/tixi,DLR-SC/tixi