extended credential_set_t interface by a cache_cert() method

allows persistent or in-memory caching of fetched certificates

src/libstrongswan/utils.c

@@ -71,6 +71,13 @@ void *return_null()
 	return NULL;
 }
 
+/**
+ * nop operation
+ */
+void nop()
+{
+}
+
 /**
  * We use a single mutex for all refcount variables. This
  * is not optimal for performance, but the critical section

src/libstrongswan/utils.h

@@ -214,6 +214,11 @@ void memxor(u_int8_t dest[], u_int8_t src[], size_t n);
  */
 void *return_null();
 
+/**
+ * No-Operation function
+ */
+void nop();
+
 /**
  * Special type to count references
  */