Move dead submodules in-tree

Signed-off-by: swurl <swurl@swurl.xyz>

externals/enet/include/enet/callbacks.h

@@ -0,0 +1,37 @@
+/** 
+ @file  callbacks.h
+ @brief ENet callbacks
+*/
+#ifndef __ENET_CALLBACKS_H__
+#define __ENET_CALLBACKS_H__
+
+#include <stdlib.h>
+
+typedef struct _ENetCallbacks
+{
+    void * (ENET_CALLBACK * malloc) (size_t size);
+    void (ENET_CALLBACK * free) (void * memory);
+    void (ENET_CALLBACK * no_memory) (void);
+} ENetCallbacks;
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/** @defgroup callbacks ENet internal callbacks
+    @{
+    @ingroup private
+*/
+
+extern void * enet_malloc (size_t);
+extern void   enet_free (void *);
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __ENET_CALLBACKS_H__ */
+