Better checking of error return codes from various thread functions. Added -dT to enable error checking mutexes in the thread library (--with-rtldebug is _not_ required). Rev: man/pike.1:1.17 Rev: src/acconfig.h:1.123 Rev: src/aclocal.m4:1.68 Rev: src/configure.in:1.713 Rev: src/main.c:1.171 Rev: src/main.h:1.22 Rev: src/pike_threadlib.h:1.39 Rev: src/threads.c:1.214