Print error codes if PR_Read fails.

nsprpub/pr/tests/sockping.c

@@ -124,7 +124,8 @@ int main()
         memset(buf, 0, sizeof(buf));
         nBytes = PR_Read(sock[0], buf, sizeof(buf));
         if (nBytes == -1) {
-            fprintf(stderr, "PR_Read failed\n");
+            fprintf(stderr, "PR_Read failed: (%d, %d)\n",
+                    PR_GetError(), PR_GetOSError());
             exit(1);
         }
         printf("ping process: received \"%s\"\n", buf);