Code tidy.

db/install.php

db/upgrade.php

question.php

stack/cas/casstring.class.php

stack/cas/connector.server.class.php

stack/cas/tests/cassession_test.php

stack/cas/tests/castext_test.php

stack/input/algebraic/tests/algebraic_test.php

stack/input/matrix/tests/matrix_test.php

stack/options.class.php

stack/potentialresponsetree.class.php

stack/questiontestresult.php

tests/walkthrough_adaptive_test.php