Adding support for Maxima 5.37.1. Problems with Maxima 5.37.2 remain.

doc/en/CAS/Plots.md

doc/en/Developer/PHP-CAS.md

doc/en/Developer/Question_state_caching.md

doc/en/Installation/testing_installation.md

lang/en/qtype_stack.php

settings.php

stack/maxima/assessment.mac

stack/maxima/stackmaxima.mac

tests/cassession_test.php

tests/input_algebraic_test.php

tests/walkthrough_adaptive_test.php

version.php