make: use the more modern wchar routines, not widec.h

*** 349,359 ****
                   */
                  stdin_buffer_start =
                    stdin_text_p = getmem(length = 1024);
                  stdin_buffer_end = stdin_text_p + length;
                  MBSTOWCS(wcs_buffer, "standard input");
!                 file_being_read = (wchar_t *) wsdup(wcs_buffer);
                  line_number = 0;
                  while ((n = read(fileno(stdin),
                                   stdin_text_p,
                                   length)) > 0) {
                          length -= n;
--- 349,359 ----
                   */
                  stdin_buffer_start =
                    stdin_text_p = getmem(length = 1024);
                  stdin_buffer_end = stdin_text_p + length;
                  MBSTOWCS(wcs_buffer, "standard input");
!                 file_being_read = (wchar_t *) wcsdup(wcs_buffer);
                  line_number = 0;
                  while ((n = read(fileno(stdin),
                                   stdin_text_p,
                                   length)) > 0) {
                          length -= n;
*** 825,835 ****
                                          INIT_STRING_FROM_STACK(include_name, include_buffer);
                                          APPEND_NAME(true_makefile_name,
                                                        &include_name,
                                                        true_makefile_name->hash.length);
  
!                                         wchar_t *slash = wsrchr(include_name.buffer.start, (int) slash_char);
                                          if (slash != NULL) {
                                                  include_name.text.p = slash + 1;
                                                  append_string(name_start,
                                                                &include_name,
                                                                name_length);
--- 825,835 ----
                                          INIT_STRING_FROM_STACK(include_name, include_buffer);
                                          APPEND_NAME(true_makefile_name,
                                                        &include_name,
                                                        true_makefile_name->hash.length);
  
!                                         wchar_t *slash = wcsrchr(include_name.buffer.start, (int) slash_char);
                                          if (slash != NULL) {
                                                  include_name.text.p = slash + 1;
                                                  append_string(name_start,
                                                                &include_name,
                                                                name_length);