maint: Include bug-reporting info in --help output

These days, many programs are including a bug-reporting address,
or better yet, a link to the project web site, at the tail of
their --help output.  However, we were not very consistent at
doing so: only qemu-nbd and qemu-qa mentioned anything, with the
latter pointing to an individual person instead of the project.

Add a new #define that sets up a uniform string, mentioning both
bug reporting instructions and overall project details, and which
a downstream vendor could tweak if they want bugs to go to a
downstream database.  Then use it in all of our binaries which
have --help output.

The canned text intentionally references http:// instead of https://
because our https website currently causes certificate errors in
some browsers.  That can be tweaked later once we have resolved the
web site issued.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20170803163353.19558-5-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qemu-io.c

@@ -262,8 +262,9 @@ static void usage(const char *name)
 "  -h, --help           display this help and exit\n"
 "  -V, --version        output version information and exit\n"
 "\n"
-"See '%s -c help' for information on available commands."
-"\n",
+"See '%s -c help' for information on available commands.\n"
+"\n"
+QEMU_HELP_BOTTOM "\n",
     name, name);
 }