a version of module symbols_in_program,
but for 32 bit Windows instead of ELF

copies a graph to a string and symbol and module names, or back,
using the symbols in the symbol table of the executable
modules must be compiled with -desc and -exl

(graph_to_string_with_descriptors doesn't)

remove bracket count in _eval_to_nf

for nodes that may contain pointers, otherwise remove_forwarding_pointers_from_graph
may use too much stack space