Add support for SHA256 and SHA512 encrypt methods. Apply RedHat's patch

shadow-4.0.18.1-sha256.patch. Thanks to Peter Vrabec. Hardly no changes
except re-indent and changes related to recent modifications (max_salt_len
in crypt_make_salt). Changes in lib/defines.h not applied (definition of
ENCRYPTMETHOD_SELECT). I will add a configure check or flag.

lib/getdef.c

@@ -84,6 +84,7 @@ static struct itemdef def_table[] = {
 	{"CHFN_AUTH", NULL},
 	{"CHSH_AUTH", NULL},
 	{"CRACKLIB_DICTPATH", NULL},
+	{"ENCRYPT_METHOD", NULL},
 	{"ENV_HZ", NULL},
 	{"ENVIRON_FILE", NULL},
 	{"ENV_TZ", NULL},