Backport new testsuite to 4.2 branch

configure.ac

tests/.gitignore

tests/Makefile.am

tests/auxiliary_variables/test1.mod

tests/block_bytecode/run_block_bytecode_tests.m

tests/block_bytecode/run_ls2003.m

tests/conditional_forecasts/fs2000_est.mod

tests/expectations/expectation.mod

tests/expectations/expectation_ss.mod

tests/expectations/expectation_ss_old.mod

tests/fs2000/fs2000d.mod

tests/gsa/ls2003.mod

tests/printMakeCheckMatlabErrMsg.m

tests/printMakeCheckOctaveErrMsg.m

tests/run_test_matlab.m

tests/run_test_octave.m

tests/steady_state/multi_leads.mod

tests/steady_state/walsh1_initval.mod

tests/steady_state/walsh1_old_ss.mod

tests/steady_state/walsh1_ssm.mod