Register POLICY_MAPPING with bssl::UniquePtr.

This will also pull in POLICY_MAPPINGS by way of STACK_OF(T) handling.

Change-Id: I8ddc9547647f8cae3800047eb58e1c83f6ae1085
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/46104
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/x509v3.h b/include/openssl/x509v3.h
index 2c9ba73..0cb9e22 100644
--- a/include/openssl/x509v3.h
+++ b/include/openssl/x509v3.h
@@ -910,6 +910,7 @@
 BORINGSSL_MAKE_DELETER(BASIC_CONSTRAINTS, BASIC_CONSTRAINTS_free)
 BORINGSSL_MAKE_DELETER(DIST_POINT, DIST_POINT_free)
 BORINGSSL_MAKE_DELETER(GENERAL_NAME, GENERAL_NAME_free)
+BORINGSSL_MAKE_DELETER(POLICY_MAPPING, POLICY_MAPPING_free)
 BORINGSSL_MAKE_DELETER(POLICYINFO, POLICYINFO_free)
 
 BSSL_NAMESPACE_END