[SPARK-16813][SQL] Remove private[sql] and private[spark] from catalyst package

[rxin]

What changes were proposed in this pull request?

The catalyst package is meant to be internal, and as a result it does not make sense to mark things as private[sql] or private[spark]. It simply makes debugging harder when Spark developers need to inspect the plans at runtime.

This patch removes all private[sql] and private[spark] visibility modifiers in org.apache.spark.sql.catalyst.

How was this patch tested?

N/A - just visibility changes.

[SparkQA]

Test build #63037 has finished for PR 14418 at commit 5fa81a9.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • case class MonotonicallyIncreasingID() extends LeafExpression with Nondeterministic
  • case class SparkPartitionID() extends LeafExpression with Nondeterministic
  • case class AggregateExpression(
  • case class CurrentDatabase() extends LeafExpression with Unevaluable
  • class GenericInternalRow(val values: Array[Any]) extends BaseGenericInternalRow
  • class AbstractScalaRowIterator[T] extends Iterator[T]

[rxin]

cc @cloud-fan

[cloud-fan]

LGTM, merging to master!

[rxin]

I've also backported this into branch-2.0 to avoid future merge conflicts.