parser: Check kernel stacking support when handling stacked transitions

Check if the current kernel supports stacking. If not, ensure that named
transitions (exec, change_profile, etc.) do not attempt to stack their
targets.

Also, set up the change_profile vector according to whether or not the
kernel supports stacking. Earlier kernels expect the policy namespace to
be in its own NUL-terminated vector element rather than passing the
entire label (namespace and profile name) as a single string to the
kernel.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>

parser/parser_common.c

@@ -73,6 +73,7 @@ int kernel_supports_dbus = 0;		/* kernel supports dbus rules */
 int kernel_supports_diff_encode = 0;	/* kernel supports diff_encode */
 int kernel_supports_signal = 0;		/* kernel supports signal rules */
 int kernel_supports_ptrace = 0;		/* kernel supports ptrace rules */
+int kernel_supports_stacking = 0;	/* kernel supports stacking */
 int conf_verbose = 0;
 int conf_quiet = 0;
 int names_only = 0;