Update SQLConf.scala

use concurrent.ConcurrentHashMap instead of util.Collections.synchronizedMap

Author: baishuo(白硕) <vc_java@hotmail.com>

Closes #1272 from baishuo/master and squashes the following commits:

51ec55d [baishuo(白硕)] Update SQLConf.scala
63da043 [baishuo(白硕)] Update SQLConf.scala
36b6dbd [baishuo(白硕)] Update SQLConf.scala
864faa0 [baishuo(白硕)] Update SQLConf.scala
593096b [baishuo(白硕)] Update SQLConf.scala
7304d9b [baishuo(白硕)] Update SQLConf.scala
843581c [baishuo(白硕)] Update SQLConf.scala
1d3e4a2 [baishuo(白硕)] Update SQLConf.scala
0740f28 [baishuo(白硕)] Update SQLConf.scala
[SPARK-2059][SQL] Add analysis checks

This replaces #1263 with a test case.

Author: Reynold Xin <rxin@apache.org>
Author: Michael Armbrust <michael@databricks.com>

Closes #1265 from rxin/sql-analysis-error and squashes the following commits:

a639e01 [Reynold Xin] Added a test case for unresolved attribute analysis.
7371e1b [Reynold Xin] Merge pull request #1263 from marmbrus/analysisChecks
448c088 [Michael Armbrust] Add analysis checks