tag: added function tag_name_parse()

Convert a string into a tag_type enum.

src/tag.h

@@ -93,6 +93,22 @@ struct tag {
 	unsigned num_items;
 };
 
+/**
+ * Parse the string, and convert it into a #tag_type.  Returns
+ * #TAG_NUM_OF_ITEM_TYPES if the string could not be recognized.
+ */
+enum tag_type
+tag_name_parse(const char *name);
+
+/**
+ * Parse the string, and convert it into a #tag_type.  Returns
+ * #TAG_NUM_OF_ITEM_TYPES if the string could not be recognized.
+ *
+ * Case does not matter.
+ */
+enum tag_type
+tag_name_parse_i(const char *name);
+
 /**
  * Creates an empty #tag.
  */