Fix break pthread detection on ancient Linux installs.

src/sbbs3/sbbscon.c

@@ -1619,6 +1619,8 @@ int main(int argc, char** argv)
 
 #ifdef _THREAD_SUID_BROKEN
 	/* check if we're using NPTL */
+/* Old (2.2) systems don't have this. */
+#ifdef _CS_GNU_LIBPTHREAD_VERSION
 	conflen=confstr (_CS_GNU_LIBPTHREAD_VERSION, NULL, 0);
 	if (conflen > 0) {
 		char *buf = alloca (conflen);
@@ -1626,6 +1628,7 @@ int main(int argc, char** argv)
 		if (strstr (buf, "NPTL"))
 			thread_suid_broken=FALSE;
 	}
+#endif
 #endif
 
 	/* Install Ctrl-C/Break signal handler here */