Changes in SQL parser:
 * Change default mode of SELECT from "lock in share mode"
   to "consistent read".
 * Remove support from SELECT for specifying "consistent read".
 * Add support in SELECT for specifying "lock in share mode".
 * Change all uses of SQL parser to specify "lock in share mode".
 * Modify syntax so that the only valid top-level statement is
   a procedure definition, since it's the only one that actually
   works.
 * Add support for lock waits.