MAINTENANCE: Automated closing of pull requests.

This commit exists to close the following pull requests on Github:

Closes #1375 (close requested by 'pwendell')
Closes #476 (close requested by 'mengxr')
Closes #2502 (close requested by 'pwendell')
Closes #2391 (close requested by 'andrewor14')
[SPARK-3371][SQL] Renaming a function expression with group by gives error

The following code gives error.
```
sqlContext.registerFunction("len", (s: String) => s.length)
sqlContext.sql("select len(foo) as a, count(1) from t1 group by len(foo)").collect()
```
Because SQl parser creates the aliases to the functions in grouping expressions with generated alias names. So if user gives the alias names to the functions inside projection then it does not match the generated alias name of grouping expression.
This kind of queries are working in Hive.
So the fix I have given that if user provides alias to the function in projection then don't generate alias in grouping expression,use the same alias.

Author: ravipesala <ravindra.pesala@huawei.com>

Closes #2511 from ravipesala/SPARK-3371 and squashes the following commits:

9fb973f [ravipesala] Removed aliases to grouping expressions.
f8ace79 [ravipesala] Fixed the testcase issue
bad2fd0 [ravipesala] SPARK-3371 : Fixed Renaming a function expression with group by gives error
SPARK-1767: Prefer HDFS-cached replicas when scheduling data-local tasks

This change reorders the replicas returned by
HadoopRDD#getPreferredLocations so that replicas cached by HDFS are at
the start of the list.  This requires Hadoop 2.5 or higher; previous
versions of Hadoop do not expose the information needed to determine
whether a replica is cached.

Author: Colin Patrick Mccabe <cmccabe@cloudera.com>

Closes #1486 from cmccabe/SPARK-1767 and squashes the following commits:

338d4f8 [Colin Patrick Mccabe] SPARK-1767: Prefer HDFS-cached replicas when scheduling data-local tasks