Minor changes in code to improve readability (freeing some character

strings earlier)

src/obidmscolumn.h

@@ -341,6 +341,8 @@ index_t obi_column_get_element_index_from_name(OBIDMS_column_p column, const cha
 /**
  * @brief Formats a date in a way that is easy to read.
  *
+ * @warning The pointer returned must be freed by the caller.
+ *
  * @param date A date.
  *
  * @returns The date formatted in a way that is easy to read.