Added the lists of opened columns and arrays in the OBIDMS structure,

and a counter in the OBIDMS column structure; fixed some bugs and
created tests for referring columns that are bound to disappear anyway.

src/obidmscolumn.h

@@ -122,6 +122,8 @@ typedef struct OBIDMS_column {
 													 * A column is writable only by its creator
 													 * until it closes it.
 													 */
+	size_t						counter;			/**< Indicates by how many threads/programs (TODO) the column is used.
+													 */
 } OBIDMS_column_t, *OBIDMS_column_p;