packet processing error (copied from pull request as issue, as it looks like parsing error related to handling of escape sequences)

[miwee]

hi. my pull request was added because of these issues in real environment:

1. "MESSAGE\nmessage-id:ID\test\c12408\c1\c1\c2\nbreadcrumbId:ID\test\c8\c8877250\c1\c1\ndestination:/topic/test\ntimestamp:1478021275091\nexpires:0\nsubscription:58\npersistent:true\npriority:4\nCamelJmsDeliveryMode:2\n\n\n\0MESS"
   this case i have fixed by remain -> {:error, remain}
2. "MESSAGE\noriginal-destination:/topic/test\nmessage-id:ID\test\c23\c1"
   and this one by considering get_headers("", _, _) as :partial

in any case thanks for your attention. and if you think that my issues actually make place and you know how to process them better way, you are welcome!

[miwee]

fixed with help from PR by yndi-halda