[#1846] Add support for AIX 5.3.

Problem description
===================

Add support for AIX 5.3 os


Changes description
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Update paver.sh script for independent repo.

Update OS administration to support AIX 5.3.

Update handling of PAM library for AIX with lazy loading since AIX shared object are stored in AIX AR Archive format and not in plain files.

Fix code duplication in 2 tests... use system test for one test and mocks for the other test.

Accounts constants only used in server were moved to server code.

OS cleanup code was improved to not stop on first error but try to clean as much as possible.


How to try and test the changes
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reviewers @alibotean 

Check that changes make sense.