disable downgrade and not enforced rule messages by default

Currently the apparmor parser warns about rules that are not enforced or
downgraded. This is a problem for distros that are not carrying the out of
tree kernel patches, as most profile loads result in warnings.

Change the behavior to not output a message unless a warn flag is passed.
This patch adds 2 different warn flags
  --warn rule-downgraded    	 # warn if a rule is downgraded
  --warn rule-not-enforced	   # warn if a rule is not enforced at all

If the warnings are desired by default the flags can be set in the
parser.conf file.

v2 of patch
- update man page
- add --warn to usage statement
- make --quiet clear warn flags

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Steve Beattie <steve@nxnw.org>

parser/mount.cc

@@ -558,7 +558,7 @@ static void warn_once(const char *name)
 {
 	static const char *warned_name = NULL;
 
-	if (warned_name != name) {
+	if ((warnflags & WARN_RULE_NOT_ENFORCED) && warned_name != name) {
 		cerr << "Warning from profile " << name << " (";
 		if (current_filename)
 			cerr << current_filename;