MTOM poor implementation causes OOM with big contents

[dam0vm3nt]

Current Base64Data implmentation here :

jaxb-ri/jaxb-ri/runtime/impl/src/main/java/org/glassfish/jaxb/runtime/v2/runtime/unmarshaller/Base64Data.java

Line 297 in b7d1ff7

// TODO: this is inefficient if the data source is note byte[] but DataHandler

handles base64 encoding inefficiently by loading the whole content in memory before encoding it to base64.