Fixed decay that broke the configure tests using rusage.c and threads.c. Also added configure tests to make it more certain that this kind of thing doesn't go by unnoticed in the future. Rev: src/configure.in:1.1016 Rev: src/pike_threadlib.h:1.61 Rev: src/rusage.c:1.45 Rev: src/svalue.h:1.146 Rev: src/threads.c:1.253