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