Create ~/.rnd with mode 0600 instead of 0666

Create ~/.rnd with mode 0600 instead of 0666

Because of a missing include <fcntl.h> we don't have O_CREATE and don't create
the file with open() using mode 0600 but fall back to using fopen() with the
default umask followed by a chmod().

Problem found by Jakub Wilk <jwilk@debian.org>.