Do not print daemon's pid after forking if a pidfile is used.

daemon.c

@@ -60,7 +60,8 @@ void daemon_init() {
             exit(1);
         } else {
             // Success !
-            printf("%d\n", pid);
+            if (!config.pidfile)
+                printf("%d\n", pid);
             exit(0);
         }
     } else {

shairport.c

@@ -88,7 +88,7 @@ void usage(char *progname) {
     printf("    -b FILL             set how full the buffer must be before audio output\n");
     printf("                        starts. This value is in frames; default %d\n", config.buffer_start_fill);
     printf("    -d, --daemon        fork (daemonise). The PID of the child process is\n");
-    printf("                        written to stdout\n");
+    printf("                        written to stdout, unless a pidfile is used.\n");
     printf("    -P, --pidfile=FILE  write daemon's pid to FILE on startup.\n");
     printf("                        Has no effect if -d is not specified\n");
     printf("    -l, --log FILE      redirect shairport's standard output to FILE\n");