Change the used 4ti2 version to 1.3.1 (rather than 1.3.2) in order to avoid diffs during regression testing

chg: also separated 4ti2 dependent tests from almost all test lists
Complete build options for Pthread API: use AX_PTHREAD instead of AC_CHECK_LIB(pthread,pthread_create)

NOTE: this is due to https://github.com/Singular/Sources/issues/571