memory: Add free wrapper and refactor project to use it

We already use wrappers for allocation, the new `xfree` function is the
equivalent for deallocation and provides a way to fully replace the malloc
implementation used by Neovim.

src/nvim/msgpack_rpc/channel.c

@@ -478,9 +478,9 @@ static void on_request_event(Event event)
                                             result,
                                             &out_buffer));
   // All arguments were freed already, but we still need to free the array
-  free(args.items);
+  xfree(args.items);
   decref(channel);
-  free(e);
+  xfree(e);
 }
 
 static bool channel_write(Channel *channel, WBuffer *buffer)
@@ -601,7 +601,7 @@ static void unsubscribe(Channel *channel, char *event)
 
   // Since the string is no longer used by other channels, release it's memory
   pmap_del(cstr_t)(event_strings, event_string);
-  free(event_string);
+  xfree(event_string);
 }
 
 /// Close the channel streams/job and free the channel resources.
@@ -655,13 +655,13 @@ static void free_channel(Channel *channel)
   pmap_free(cstr_t)(channel->subscribed_events);
   kv_destroy(channel->call_stack);
   kv_destroy(channel->delayed_notifications);
-  free(channel);
+  xfree(channel);
 }
 
 static void close_cb(uv_handle_t *handle)
 {
-  free(handle->data);
-  free(handle);
+  xfree(handle->data);
+  xfree(handle);
 }
 
 static Channel *register_channel(void)
@@ -738,7 +738,7 @@ static WBuffer *serialize_request(uint64_t channel_id,
   WBuffer *rv = wstream_new_buffer(xmemdup(sbuffer->data, sbuffer->size),
                                    sbuffer->size,
                                    refcount,
-                                   free);
+                                   xfree);
   msgpack_sbuffer_clear(sbuffer);
   api_free_array(args);
   return rv;
@@ -757,7 +757,7 @@ static WBuffer *serialize_response(uint64_t channel_id,
   WBuffer *rv = wstream_new_buffer(xmemdup(sbuffer->data, sbuffer->size),
                                    sbuffer->size,
                                    1,  // responses only go though 1 channel
-                                   free);
+                                   xfree);
   msgpack_sbuffer_clear(sbuffer);
   api_free_object(arg);
   return rv;

src/nvim/msgpack_rpc/remote_ui.c

@@ -48,9 +48,9 @@ void remote_ui_disconnect(uint64_t channel_id)
   // destroy pending screen updates
   api_free_array(data->buffer);
   pmap_del(uint64_t)(connected_uis, channel_id);
-  free(ui->data);
+  xfree(ui->data);
   ui_detach(ui);
-  free(ui);
+  xfree(ui);
 }
 
 static Object remote_ui_attach(uint64_t channel_id, uint64_t request_id,

src/nvim/msgpack_rpc/server.c

@@ -57,7 +57,7 @@ bool server_init(void)
   if (!os_getenv(LISTEN_ADDRESS_ENV_VAR)) {
     char *listen_address = (char *)vim_tempname();
     os_setenv(LISTEN_ADDRESS_ENV_VAR, listen_address, 1);
-    free(listen_address);
+    xfree(listen_address);
   }
 
   return server_start((char *)os_getenv(LISTEN_ADDRESS_ENV_VAR)) == 0;
@@ -256,10 +256,10 @@ static void connection_cb(uv_stream_t *server, int status)
 
 static void free_client(uv_handle_t *handle)
 {
-  free(handle);
+  xfree(handle);
 }
 
 static void free_server(uv_handle_t *handle)
 {
-  free(handle->data);
+  xfree(handle->data);
 }