kernel-interface: Add feature to indicate if query_sa() returns last use time

Currently supported by libipsec and PF_KEY on macOS (FreeBSD, like Linux,
reports the time the SA was first used in sadb_lifetime_usetime - it also
triggers rekeyings based on that, which Linux doesn't, it also triggers
them if an SA is never used).

src/frontends/android/app/src/main/jni/libandroidbridge/kernel/android_ipsec.c

@@ -46,6 +46,12 @@ static void expire(uint8_t protocol, uint32_t spi, host_t *dst, bool hard)
 	charon->kernel->expire(charon->kernel, protocol, spi, dst, hard);
 }
 
+METHOD(kernel_ipsec_t, get_features, kernel_feature_t,
+	private_kernel_android_ipsec_t *this)
+{
+	return KERNEL_SA_USE_TIME;
+}
+
 METHOD(kernel_ipsec_t, get_spi, status_t,
 	private_kernel_android_ipsec_t *this, host_t *src, host_t *dst,
 	uint8_t protocol, uint32_t *spi)
@@ -166,6 +172,7 @@ kernel_android_ipsec_t *kernel_android_ipsec_create()
 	INIT(this,
 		.public = {
 			.interface = {
+				.get_features = _get_features,
 				.get_spi = _get_spi,
 				.get_cpi = _get_cpi,
 				.add_sa  = _add_sa,