Don't report unclosed comments as "no newline at end of file". If we get EOF in the "middle" of a line but there's a newline at the end of the buffer we've got, it's because we're in the middle of a comment. So, say so.

+
−#define a() x
+
−a()
+
−a ()
+
−#define b(p) p
+
−x/**/b(1)/**/x
+
−x/**/b (1)/**/x
+
−x/**/b()/**/x
+
−#define c(p,q) p/**/q
+
−x/**/c(1,2)/**/x
+
−x/**/c(1)/**/x
+
−x/**/c()/**/x