parser: Fix parsing of patches with a trailing no-newline marker

If a patch ends with a "No newline at end of file" marker, it is
incorrectly considered part of the comment.

Add a testcase which shows the bug, and then fix the parser. The parser
fix is hopefully sufficiently specific so as to not break any other
unrelated case. But ..

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>