Add some missing Diff::Line line origin check helpers.
Add some missing Diff::Line line origin check helpers.

libgit2/rugged,libgit2/rugged,tpickett66/rugged,saraid/rugged,Acidburn0zzz/rugged,saraid/rugged,tpickett66/rugged,libgit2/rugged,tpickett66/rugged,Acidburn0zzz/rugged,Acidburn0zzz/rugged,saraid/rugged