IMPALA-1069: Cap the maximum number of io buffers the iomgr will hold onto.

Change-Id: I20704e4b10a3c4e908c96577dc65c01cceaf30c4
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3713
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins
IMPALA-1121: Fix joins on decimal columns with different precision/scale.

Change-Id: Ibac69763e28ad33ef41d000b5dd74fc73c74b73a
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3726
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Tested-by: jenkins
IMPALA-1128: Fix Type.getAssignmentCompatibleType to always be consistent.

Before, in the case where two types were equally compatible (e.g BIGINT and decimal(19,0)),
we'd pick an arbitrary one as the compatible type depending on the order of the input
arguments. This mostly works but makes it harder to verify and reason about.

Change-Id: I4b19da8ef9c894065bc22809967497b927d4e081
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3727
Reviewed-by: Marcel Kornacker <marcel@cloudera.com>
Tested-by: jenkins
IMPALA-639: Fix per node peak mem usage reporting.

Change-Id: Ie130df4f9434ae8d9ff500afc41a17010927338a
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3729
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins