warning: multi-line comment (why?)

[Joern Rennecke]

> To be consistent we should also whitespace-skip \v and \f.  No special
> tab handling is needed - it's only there to keep track of columns for
> warnings, and since we're a line comment there are not going to be any
> warnings on the line (trigraph warnings are now turned off).
> is_nvspace does all that for you.

What happens when the line is the last line in the file and is missing
a newline?
What happens if it's the last line and it ends with a backslash / newline?