[SPARK-6134][SQL] Fix wrong datatype for casting FloatType and default...

[SPARK-6134][SQL] Fix wrong datatype for casting FloatType and default LongType value in defaultPrimitive

In `CodeGenerator`, the casting on `FloatType` should use `FloatType` instead of `IntegerType`.

Besides, `defaultPrimitive` for `LongType` should be `-1L` instead of `1L`.

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #4870 from viirya/codegen_type and squashes the following commits:

76311dd [Liang-Chi Hsieh] Fix wrong datatype for casting on FloatType. Fix the wrong value for LongType in defaultPrimitive.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala

@@ -259,7 +259,7 @@ abstract class CodeGenerator[InType <: AnyRef, OutType <: AnyRef] extends Loggin
         child.castOrNull(c => q"$c.toDouble", DoubleType)
 
       case Cast(child @ NumericType(), FloatType) =>
-        child.castOrNull(c => q"$c.toFloat", IntegerType)
+        child.castOrNull(c => q"$c.toFloat", FloatType)
 
       // Special handling required for timestamps in hive test cases since the toString function
       // does not match the expected output.
@@ -626,7 +626,7 @@ abstract class CodeGenerator[InType <: AnyRef, OutType <: AnyRef] extends Loggin
     case FloatType => ru.Literal(Constant(-1.0.toFloat))
     case StringType => ru.Literal(Constant("<uninit>"))
     case ShortType => ru.Literal(Constant(-1.toShort))
-    case LongType => ru.Literal(Constant(1L))
+    case LongType => ru.Literal(Constant(-1L))
     case ByteType => ru.Literal(Constant(-1.toByte))
     case DoubleType => ru.Literal(Constant(-1.toDouble))
     case DecimalType() => q"org.apache.spark.sql.types.Decimal(-1)"