[SPARK-14639] [PYTHON] [R] Add `bround` function in Python/R.

## What changes were proposed in this pull request?

This issue aims to expose Scala `bround` function in Python/R API.
`bround` function is implemented in SPARK-14614 by extending current `round` function.
We used the following semantics from Hive.
```java
public static double bround(double input, int scale) {
    if (Double.isNaN(input) || Double.isInfinite(input)) {
      return input;
    }
    return BigDecimal.valueOf(input).setScale(scale, RoundingMode.HALF_EVEN).doubleValue();
}
```

After this PR, `pyspark` and `sparkR` also support `bround` function.

**PySpark**
```python
>>> from pyspark.sql.functions import bround
>>> sqlContext.createDataFrame([(2.5,)], ['a']).select(bround('a', 0).alias('r')).collect()
[Row(r=2.0)]
```

**SparkR**
```r
> df = createDataFrame(sqlContext, data.frame(x = c(2.5, 3.5)))
> head(collect(select(df, bround(df$x, 0))))
  bround(x, 0)
1            2
2            4
```

## How was this patch tested?

Pass the Jenkins tests (including new testcases).

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #12509 from dongjoon-hyun/SPARK-14639.

1 files changed, 5 insertions, 0 deletions

diff --git a/R/pkg/inst/tests/testthat/test_sparkSQL.R b/R/pkg/inst/tests/testthat/test_sparkSQL.R
index 2f65484fcb..b923ccf6bb 100644
--- a/R/pkg/inst/tests/testthat/test_sparkSQL.R
+++ b/R/pkg/inst/tests/testthat/test_sparkSQL.R
@@ -1087,6 +1087,11 @@ test_that("column functions", {
   expect_equal(collect(select(df, last(df$age, TRUE)))[[1]], 19)
   expect_equal(collect(select(df, last("age")))[[1]], 19)
   expect_equal(collect(select(df, last("age", TRUE)))[[1]], 19)
+
+  # Test bround()
+  df <- createDataFrame(sqlContext, data.frame(x = c(2.5, 3.5)))
+  expect_equal(collect(select(df, bround(df$x, 0)))[[1]][1], 2)
+  expect_equal(collect(select(df, bround(df$x, 0)))[[1]][2], 4)
 })
 
 test_that("column binary mathfunctions", {