encoding/decoding of programs implemented

Rev: src/builtin_functions.c:1.101
Rev: src/compilation.h:1.9
Rev: src/encode.c:1.20
Rev: src/gc.c:1.36
Rev: src/object.c:1.48
Rev: src/object.h:1.19
Rev: src/program.c:1.87
Rev: src/program.h:1.41
Rev: src/program_areas.h:1.5