[SPARK-18333] [SQL] Revert hacks in parquet and orc reader to support case insensitive resolution

[ericl]

What changes were proposed in this pull request?

These are no longer needed after https://issues.apache.org/jira/browse/SPARK-17183

cc @cloud-fan

How was this patch tested?

Existing parquet and orc tests.

[SparkQA]

Test build #68296 has finished for PR 15799 at commit 8921868.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • case class Md5(child: Expression) extends UnaryExpression with ImplicitCastInputTypes
  • case class Sha2(left: Expression, right: Expression)
  • case class Sha1(child: Expression) extends UnaryExpression with ImplicitCastInputTypes
  • case class Crc32(child: Expression) extends UnaryExpression with ImplicitCastInputTypes
  • abstract class HashExpression[E] extends Expression
  • abstract class InterpretedHashFunction
  • case class Murmur3Hash(children: Seq[Expression], seed: Int) extends HashExpression[Int]
  • case class XxHash64(children: Seq[Expression], seed: Long) extends HashExpression[Long]
  • case class HiveHash(children: Seq[Expression]) extends HashExpression[Int]
  • abstract class RDG extends UnaryExpression with ExpectsInputTypes with Nondeterministic
  • case class Rand(child: Expression) extends RDG
  • case class Randn(child: Expression) extends RDG

[ericl]

jenkins retest this please

[cloud-fan]

LGTM, can you also point out which PR added this hack? thanks.

[SparkQA]

Test build #68304 has finished for PR 15799 at commit 8921868.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • case class Md5(child: Expression) extends UnaryExpression with ImplicitCastInputTypes
  • case class Sha2(left: Expression, right: Expression)
  • case class Sha1(child: Expression) extends UnaryExpression with ImplicitCastInputTypes
  • case class Crc32(child: Expression) extends UnaryExpression with ImplicitCastInputTypes
  • abstract class HashExpression[E] extends Expression
  • abstract class InterpretedHashFunction
  • case class Murmur3Hash(children: Seq[Expression], seed: Int) extends HashExpression[Int]
  • case class XxHash64(children: Seq[Expression], seed: Long) extends HashExpression[Long]
  • case class HiveHash(children: Seq[Expression]) extends HashExpression[Int]
  • abstract class RDG extends UnaryExpression with ExpectsInputTypes with Nondeterministic
  • case class Rand(child: Expression) extends RDG
  • case class Randn(child: Expression) extends RDG

[ericl]

The hacks were added in #14690

[SparkQA]

Test build #68374 has finished for PR 15799 at commit 7f02648.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[cloud-fan]

LGTM

[cloud-fan]

merging to master/2.1