Fix issue 4884, preventing a crash in the socket code when python is compiled

with llvm-gcc and run with a glibc <2.10.

Modules/socketmodule.c

@@ -3334,7 +3334,11 @@ socket_gethostbyaddr(PyObject *self, PyObject *args)
 #ifdef HAVE_GETHOSTBYNAME_R_3_ARG
 	struct hostent_data data;
 #else
-	char buf[16384];
+	/* glibcs up to 2.10 assume that the buf argument to
+	   gethostbyaddr_r is 8-byte aligned, which at least llvm-gcc
+	   does not ensure. The attribute below instructs the compiler
+	   to maintain this alignment. */
+	char buf[16384] Py_ALIGNED(8);
 	int buf_len = (sizeof buf) - 1;
 	int errnop;
 #endif