[db] Generic fixup + align fixing up between mfi, pli and queue_item

The idea here is to make sure the fixing up of tags is done in a consistent
manner. For strings, this means stuff like trimming and empty strings -> null
are applied the same unless there are special exception rules set. It also
means that defaults are applied the same across structs, e.g. "Unknown artist"
for both mfi->artist and queue_item->artist.

The change is also necessary because we want to remove trimming from the sql
query and instead implement it ourselves.

src/db.h

@@ -425,8 +425,7 @@ struct directory_enum {
   void *stmt;
 };
 
-struct db_queue_item
-{
+struct db_queue_item {
   /* A unique id for this queue item. If the same item appears multiple
      times in the queue each corresponding queue item has its own id. */
   uint32_t id;
@@ -434,18 +433,16 @@ struct db_queue_item
   /* Id of the file/item in the files database */
   uint32_t file_id;
 
-  /* Length of the item in ms */
-  uint32_t song_length;
+  uint32_t pos;
+  uint32_t shuffle_pos;
 
   /* Data type of the item */
   enum data_kind data_kind;
   /* Media type of the item */
   enum media_kind media_kind;
 
-  uint32_t seek;
-
-  uint32_t pos;
-  uint32_t shuffle_pos;
+  /* Length of the item in ms */
+  uint32_t song_length;
 
   char *path;
   char *virtual_path;
@@ -453,7 +450,6 @@ struct db_queue_item
   char *title;
   char *artist;
   char *album_artist;
-  char *composer;
   char *album;
   char *genre;
 
@@ -471,8 +467,15 @@ struct db_queue_item
   char *artwork_url;
 
   uint32_t queue_version;
+
+  char *composer;
+
+  /* Not saved in queue table */
+  uint32_t seek;
 };
 
+#define qi_offsetof(field) offsetof(struct db_queue_item, field)
+
 struct db_queue_add_info
 {
   int queue_version;
@@ -510,12 +513,6 @@ free_query_params(struct query_params *qp, int content_only);
 void
 free_queue_item(struct db_queue_item *queue_item, int content_only);
 
-void
-unicode_fixup_mfi(struct media_file_info *mfi);
-
-void
-fixup_tags_mfi(struct media_file_info *mfi);
-
 /* Maintenance and DB hygiene */
 void
 db_hook_post_scan(void);