Enhance PHPUnit tests

htdocs/includes/login/functions_dolibarr.php

htdocs/includes/login/functions_empty.php

htdocs/includes/login/functions_forceuser.php

htdocs/includes/login/functions_http.php

htdocs/includes/login/functions_ldap.php

htdocs/includes/login/functions_myopenid.php

test/phpunit/AdherentTest.php

test/phpunit/BuildDocTest.php

test/phpunit/CMailFileTest.php

test/phpunit/CategorieTest.php

test/phpunit/ChargeSocialesTest.php

test/phpunit/CommandeFournisseurTest.php

test/phpunit/CommandeTest.php

test/phpunit/CommonObjectTest.php

test/phpunit/CompanyBankAccountTest.php

test/phpunit/ContratTest.php

test/phpunit/DateLibTest.php

test/phpunit/DiscountTest.php

test/phpunit/ExportTest.php

test/phpunit/FactureFournisseurTest.php