CMSG_DATA.3: Fix formatting of printf escape sequences

[0mp]

Summary

CMSG_DATA.3: Fix formatting of printf escape sequences

Escape sequences like "\n" have to be escaped twice in examples in our
mdoc(7)-based manual pages in order to be displayed properly. The problem is that otherwise they are interpreted by mdoc(7) resulting in:

    printf("parent: received '%s'0, buf);

being printed instead of:

    printf("parent: received '%s'\n", buf);


MFC after:	2 weeks
MFC to:		stable/12

[bcr]

Looks good. You don't necessarily need to specify which branch you are planning to MFC to.
It's not wrong either.

[0mp]

In D24056#528964, @bcr wrote:

Looks good. You don't necessarily need to specify which branch you are planning to MFC to.
It's not wrong either.

I did it because I know that merging it back to stable/11 is not going to happen.

Should I still include it or just skip it as it looks weird?

[bcr]

Just skip it.