libsepol: Add ability to convert binary policy to policy.conf file

It would sometimes be helpful for debugging or verification purposes
to be able to convert a binary policy to a human-readable form.

Create new function, sepol_kernel_policydb_to_conf(), that takes a
policydb created from a binary policy and writes a policy.conf file
to the provided FILE pointer.

Signed-off-by: James Carter <jwcart2@tycho.nsa.gov>

libsepol/include/sepol/kernel_to_conf.h

@@ -0,0 +1,5 @@
+#include <stdlib.h>
+
+#include <sepol/policydb/policydb.h>
+
+int sepol_kernel_policydb_to_conf(FILE *fp, struct policydb *pdb);