adding extensions to support more RDBMS types

git-svn-id: https://svn.wso2.org/repos/wso2/carbon/platform/trunk@178372 a5903396-d722-0410-b921-86c7d4935375
code cleanup

git-svn-id: https://svn.wso2.org/repos/wso2/carbon/platform/trunk@178373 a5903396-d722-0410-b921-86c7d4935375