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>

linux-user/main.c

@@ -4136,7 +4136,9 @@ static void usage(int exitcode)
            "    -E var1=val2,var2=val2 -U LD_PRELOAD,LD_DEBUG\n"
            "    QEMU_SET_ENV=var1=val2,var2=val2 QEMU_UNSET_ENV=LD_PRELOAD,LD_DEBUG\n"
            "Note that if you provide several changes to a single variable\n"
-           "the last change will stay in effect.\n");
+           "the last change will stay in effect.\n"
+           "\n"
+           QEMU_HELP_BOTTOM "\n");
 
     exit(exitcode);
 }