WIP fix to addredd issue #586.

locallib.php

stack/cas/parsingrules/110_protect_strings.filter.php

stack/cas/parsingrules/997_string_security.filter.php

stack/cas/parsingrules/README

stack/cas/parsingrules/parsingrule.factory.php

stack/input/inputbase.class.php

tests/ast_filter_110_protect_strings.auto-generated_test.php

tests/fixtures/maximacorrectiveparser.class.php

tests/input_algebraic_test.php

tests/input_equiv_test.php

tests/input_string_test.php

tests/input_varmatrix_test.php