Better names for the YES, NO and UNKNOWN flags to avoid clashes. Rev: src/acconfig.h:1.115 Rev: src/builtin_functions.c:1.475 Rev: src/configure.in:1.685 Rev: src/gc.c:1.206 Rev: src/modules/system/system.c:1.140 Rev: src/threads.c:1.201 Rev: src/threads.h:1.123