Set newline parameter on standard streams to ensure no mangling of line endings.

Now that src is handling binary data, the newline parameter on the standard I/O streams needs to be set to ensure that Python doesn't mangle line endings. I saw this during reposurgeon testing and added this parameter there to fix the same issue.

Update: added newline test to srctest. The cat portion of this test is disabled for sccs backend because of failure similar to its failure on the binary cat test.