api: auto generate api function wrappers for viml

src/nvim/api/private/dispatch.h

@@ -3,13 +3,15 @@
 
 #include "nvim/api/private/defs.h"
 
+typedef Object (*ApiDispatchWrapper)(uint64_t channel_id,
+                                     uint64_t request_id,
+                                     Array args,
+                                     Error *error);
+
 /// The rpc_method_handlers table, used in msgpack_rpc_dispatch(), stores
 /// functions of this type.
 typedef struct {
-  Object (*fn)(uint64_t channel_id,
-               uint64_t request_id,
-               Array args,
-               Error *error);
+  ApiDispatchWrapper fn;
   bool async;  // function is always safe to run immediately instead of being
                // put in a request queue for handling when nvim waits for input.
 } MsgpackRpcRequestHandler;