Quantile: Suppress integer overflow
Quantile: Suppress integer overflow

Jira: MADLIB-601

quantile_big used INT/FLOAT to store the number of rows in the table.
If the number of rows in the table exceeds 2^31, the integer will
overflow.  At the same time, cast count(*) to FLOAT may cause issues.

To fix it, we use INT8 to store the number of rows in the table.

orhankislal/madlib,madlib/madlib,iyerr3/incubator-madlib,hpandeycodeit/incubator-madlib,apache/incubator-madlib,hpandeycodeit/incubator-madlib,mktal/incubator-madlib,njayaram2/incubator-madlib,mktal/incubator-madlib,lmatthieu/incubator-madlib,madlib/madlib,iyerr3/incubator-madlib,hpandeycodeit/incubator-madlib,njayaram2/incubator-madlib,lmatthieu/incubator-madlib,njayaram2/madlib,rashmi815/incubator-madlib,rashmi815/incubator-madlib,madlib/madlib,orhankislal/madlib,orhankislal/madlib,rvs/incubator-madlib,rashmi815/incubator-madlib,rvs/incubator-madlib,mktal/incubator-madlib,iyerr3/incubator-madlib,njayaram2/incubator-madlib,cooper-sloan/incubator-madlib,rashmi815/incubator-madlib,hpandeycodeit/incubator-madlib,apache/incubator-madlib,iyerr3/incubator-madlib,apache/incubator-madlib,njayaram2/incubator-madlib,orhankislal/incubator-madlib,njayaram2/incubator-madlib,orhankislal/incubator-madlib,orhankislal/incubator-madlib,rvs/incubator-madlib,cooper-sloan/incubator-madlib,apache/incubator-madlib,madlib/madlib,mktal/incubator-madlib,njayaram2/madlib,orhankislal/madlib,rashmi815/incubator-madlib,lmatthieu/incubator-madlib,cooper-sloan/incubator-madlib,orhankislal/incubator-madlib,orhankislal/incubator-madlib,orhankislal/madlib,rvs/incubator-madlib,lmatthieu/incubator-madlib,njayaram2/madlib,njayaram2/madlib,rvs/incubator-madlib,njayaram2/madlib,lmatthieu/incubator-madlib,cooper-sloan/incubator-madlib,madlib/madlib,apache/incubator-madlib,cooper-sloan/incubator-madlib,hpandeycodeit/incubator-madlib,iyerr3/incubator-madlib,mktal/incubator-madlib