HPCC-8882 Common up and clean up rowset releasing code.

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
HPCC-8882 Make eclrtl depend on roxiemem and remove row callback

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
HPCC-8882 Switch use using the Roxie macros and remove a cloned class

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
HPCC-8882 Move commonext into thorhelper and thorutil

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
HPCC-8882 Provide rudimentary documentation for eclrtl and thorhelper

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #4038 from ghalliday/issue8882b

HPCC-8882 More rationalisation of the dll structure

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>