Replace all remaining uses of error_msg_() and remove global errbuf

This concludes the previous work done in commits:

* 2594dac
* 5727160
* 702f2fd
* 778f9cc
* fab91f1
* 7da81f2
* f1ff10b

src/buffer.c

@@ -106,7 +106,7 @@ void free_blocks(Buffer *buffer)
 static void buffer_unlock_and_free(EditorState *e, Buffer *buffer)
 {
     if (buffer->locked) {
-        unlock_file(&e->locks_ctx, e->err, buffer->abs_filename);
+        unlock_file(&e->locks_ctx, &e->err, buffer->abs_filename);
     }
 
     free_changes(&buffer->change_head);
@@ -405,7 +405,7 @@ void buffer_setup(EditorState *e, Buffer *buffer)
     if (buffer->options.detect_indent && filename) {
         detect_indent(buffer);
     }
-    sanity_check_local_options(e->err, &buffer->options);
+    sanity_check_local_options(&e->err, &buffer->options);
 }
 
 void buffer_count_blocks_and_bytes(const Buffer *buffer, uintmax_t counts[2])

src/change.c

@@ -234,7 +234,7 @@ bool undo(View *view)
             count++;
         }
         if (count > 1) {
-            ErrorBuffer *ebuf = view->window->editor->err;
+            ErrorBuffer *ebuf = &view->window->editor->err;
             info_msg(ebuf, "Undid %lu changes", count);
         }
     } else {
@@ -247,7 +247,7 @@ bool undo(View *view)
 
 bool redo(View *view, unsigned long change_id)
 {
-    ErrorBuffer *ebuf = view->window->editor->err;
+    ErrorBuffer *ebuf = &view->window->editor->err;
     Change *change = view->buffer->cur_change;
     view_reset_preferred_x(view);
     if (!change->prev) {