DERBY-6063: Access static variables by class name in TabInfoImpl, InsertResultSet and ControlRow

Replaced occurrences of accessing static variables via instances with access via class names.
Removed unused meothod in ControlRow.
Removed a few unused local variables.

Patch file: derby-6063-1a_statics-by-class_and_unused_method.diff


git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1441396 13f79535-47bb-0310-9956-ffa450edef68