Localise tex output of Maxima's True/False for issue #595.

lang/en/qtype_stack.php

locallib.php

stack/maxima/rtest_assessment_simpboth.mac

stack/maxima/stacktex.lisp

tests/cassession2_test.php

tests/castext_test.php

tests/fixtures/inputfixtures.class.php

tests/input_algebraic_test.php

tests/input_boolean_rendering_test.php

tests/input_boolean_validation_test.php