Terminate messages with a newline so that dialog box won't overwrite messages.

Should be pulled up to netbsd-7 (and netbsd-6) branches.
Fix ptrace %rcx corruption when pthread_errno() is used. Small example:
    #include <sys/types.h>
    #include <stdio.h>
    #include <sys/ptrace.h>
    int main(void) { ptrace(18, getpid(), NULL, 0xabcd); }
The -lpthread cases pases 0 instead of 0xabcd
Don't read past the end when the data is exactly the right size. Reported
by tedu @ openbsd in tech-userlevel. Thanks!
knf, no functional change.
Trivial build fix for no options SYSCTL_INCLUDE_DESCR case, to
avoid -Werror.
OK christos@ and riastradh@