main_memory = 12000000 % words of inimemory available; also applies to inimf&mp
extra_mem_top = 10000000 % extra high memory for chars, tokens, etc.
extra_mem_bot = 10000000 % extra low memory for boxes, glue, breakpoints, etc.
save_size = 150000 % for saving values outside current group
stack_size = 150000 % simultaneous input sources
