DERBY-6202: Fix bug involving upgrade, triggers, and dropped columns.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1476235 13f79535-47bb-0310-9956-ffa450edef68
DERBY-6206: Encapsulate constants and names used for isolation levels.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1476291 13f79535-47bb-0310-9956-ffa450edef68
DERBY-6206: Clone timestamps in XPLAIN code to fix mutability problems.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1476344 13f79535-47bb-0310-9956-ffa450edef68
DERBY-6169: Reduce visibility of classes and methods under impl/sql

- Change visibility of all classes generated from sqlgrammar.jj to
  package protected.

- Make CompilerContextImpl.getParameterTypes() package protected since
  it's never called from outside the package.
DERBY-6169: Reduce visibility of classes and methods under impl/sql

- Make all fields of CreateViewNode and BasicProviderInfo private.

- Make BasicProviderInfo's constructor package private.

- Make CreateViewNode.getProviderInfo() return an immutable list
  instead of the actual array to prevent accidental modification by
  the caller.
DERBY-6169: Reduce visibility of classes and methods under impl/sql

Remove two unused methods in the TriggerExecutionContext interface,
and their implementations in InternalTriggerExecutionContext. This
also made it possible to remove some fields that were only used by the
removed methods, and also corresponding fields and parameters in
neighbour classes.