Add support for libcups v3 client credentials API.

cups/cups-private.h

@@ -166,8 +166,7 @@ typedef struct _cups_globals_s		// CUPS global state data
   void			*oauth_data;	// OAuth user data
   cups_password_cb2_t	password_cb;	// Password callback
   void			*password_data;	// Password user data
-  _http_tls_credentials_t *tls_credentials;
-					// Default client credentials, if any
+  _http_tls_credentials_t *credentials;	// Default client credentials, if any
   cups_client_cert_cb_t	client_cert_cb;	// Client certificate callback @deprecated@
   void			*client_cert_data;
 					// Client certificate user data @deprecated@

cups/globals.c

@@ -425,7 +425,7 @@ cups_globals_free(_cups_globals_t *cg)	/* I - Pointer to global data */
 
   httpClose(cg->http);
 
-  _httpFreeCredentials(cg->tls_credentials);
+  _httpFreeCredentials(cg->credentials);
 
   cupsFileClose(cg->stdio_files[0]);
   cupsFileClose(cg->stdio_files[1]);

cups/usersys.c

@@ -330,6 +330,34 @@ cupsSetClientCertCB(
 }
 
 
+//
+// 'cupsSetClientCredentials()' - Set the default credentials to be used for TLS connections.
+//
+// Note: The default credentials are tracked separately for each thread in a
+// program. Multi-threaded programs that override the setting need to do so in
+// each thread for the same setting to be used.
+//
+// @since CUPS 2.5@
+//
+
+bool					// O - `true` on success, `false` on failure
+cupsSetClientCredentials(
+    const char *credentials,		// I - PEM-encoded X.509 credentials string
+    const char *key)			// I - PEM-encoded private key
+{
+  _cups_globals_t *cg = _cupsGlobals();	// Pointer to library globals
+
+
+  if (!credentials || !*credentials || !key || !*key)
+    return (false);
+
+  _httpFreeCredentials(cg->credentials);
+  cg->credentials = _httpCreateCredentials(credentials, key);
+
+  return (cg->credentials != NULL);
+}
+
+
 /*
  * 'cupsSetCredentials()' - Set the default credentials to be used for SSL/TLS
  *			    connections.