atexit() and weak arrays implemented

Rev: src/array.c:1.46
Rev: src/array.h:1.17
Rev: src/builtin_functions.c:1.166
Rev: src/encode.c:1.31
Rev: src/main.c:1.70
Rev: src/object.c:1.70
Rev: src/signal_handler.c:1.123
Rev: src/signal_handler.h:1.7