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/parser_common.c

@@ -80,6 +80,7 @@ int current_lineno = 1;
 int option = OPTION_ADD;
 
 dfaflags_t dfaflags = (dfaflags_t)(DFA_CONTROL_TREE_NORMAL | DFA_CONTROL_TREE_SIMPLE | DFA_CONTROL_MINIMIZE | DFA_CONTROL_DIFF_ENCODE);
+dfaflags_t warnflags = 0;
 
 char *subdomainbase = NULL;
 const char *progname = __FILE__;