Deprecated functions

[nrdsp]

I am getting the following errors concerning functions ppdOpenFile, ppdMarkDefaults, and ppdFirstOption:

cups-pdf.c: In function 'read_config_ppd':
cups-pdf.c:282:3: warning: 'ppdOpenFile' is deprecated: Use cupsCopyDestInfo and friends instead. [8;;https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wdeprecated-declarations-Wdeprecated-declarations8;;]
  282 |   ppd_file = ppdOpenFile(ppd_name);
      |   ^~~~~~~~
In file included from cups-pdf.c:60:
/nix/store/3flv6k8sbl521f5980w4lpbxh2dfxvx1-cups-2.4.2-dev/include/cups/ppd.h:389:26: note: declared here
  389 | extern ppd_file_t       *ppdOpenFile(const char *filename) _CUPS_DEPRECATED_1_6_MSG("Use cupsCopyDestInfo and friends instead.");
      |                          ^~~~~~~~~~~
cups-pdf.c:287:3: warning: 'ppdMarkDefaults' is deprecated: Use cupsCopyDestInfo and friends instead. [8;;https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wdeprecated-declarations-Wdeprecated-declarations8;;]
  287 |   ppdMarkDefaults(ppd_file);
      |   ^~~~~~~~~~~~~~~
In file included from cups-pdf.c:60:
/nix/store/3flv6k8sbl521f5980w4lpbxh2dfxvx1-cups-2.4.2-dev/include/cups/ppd.h:384:25: note: declared here
  384 | extern void             ppdMarkDefaults(ppd_file_t *ppd) _CUPS_DEPRECATED_1_6_MSG("Use cupsCopyDestInfo and friends instead.");
      |                         ^~~~~~~~~~~~~~~
cups-pdf.c:289:3: warning: 'ppdFirstOption' is deprecated: Use cupsCopyDestInfo and friends instead. [8;;https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wdeprecated-declarations-Wdeprecated-declarations8;;]
  289 |   option = ppdFirstOption(ppd_file);
      |   ^~~~~~
In file included from cups-pdf.c:60: