nt/*.c: Use const char*; remove unused code.

nt/*.c: Use const char*; remove unused code.

* addpm.c (entry, add_registry, main):
* addsection.c (file_data, open_input_file, open_output_file)
  (find_section, PTR_TO_OFFSET, copy_executable_and_add_section)
  (COPY_CHUNK):
* cmdproxy.c (vfprintf, fprintf, printf, fail, warn, skip_space)
  (skip_nonspace, get_next_token, search_dir, make_absolute)
  (spawn, main):
* preprep.c (file_data, open_input_file, open_output_file)
  (open_inout_file, find_section, PTR_TO_OFFSET, COPY_CHUNK, main):
  Use const char*.

* cmdproxy.c (stdin): Don't define, not used.
  (main): Don't assign remlen after last use.