Remove known references to internal architechture from the Impala respository.

Change-Id: I7a160d00937cd4b5ceab5ce8493740569142702a
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/4928
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Reviewed-by: Ippokratis Pandis <ipandis@cloudera.com>
Tested-by: jenkins