Intext 118: Fix message part splitting for long messages containing newlines

This pull request concerns INTEXT-118 in spring-integration-smpp. 

Long messages that contain newlines were not split into parts of correct size.  

The test in the pull request demonstrates that no matter if the message contains newlines or not the splitting results in correctly sized message parts.

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These lines should just be deleted. 

I used it for system.out "logging" since there was no log4j dependency I could use in the test scope. The println is disabled by default, and can be enabled by setting -Dshow_test_output=true when run from the command line.  But the lines doing the print should really just be deleted. I missed those lines when committing.