LOCK TABLE support [CR 444921]

As of 12.7 ESD #3, the LOCK TABLE statement supports acquiring WRITE locks on a set of tables. The LOCK TABLE statement also allows enqueuing for READ, WRITE, and EXCLUSIVE locks for a specified time period. For updates to LOCK TABLE syntax and usage in Chapter 6, “SQL Statements,” see “LOCK TABLE support [CR 480880, CR 472791, CR 463196, 444921]”.