config-win32: Fix warning HAVE_WINSOCK2_H undefined

lib/config-win32.h

@@ -627,7 +627,8 @@ Vista
 /* Define if struct sockaddr_in6 has the sin6_scope_id member. */
 #define HAVE_SOCKADDR_IN6_SIN6_SCOPE_ID 1
 
-#if HAVE_WINSOCK2_H && defined(_WIN32_WINNT) && (_WIN32_WINNT >= 0x0600)
+#if defined(HAVE_WINSOCK2_H) && defined(_WIN32_WINNT) && \
+    (_WIN32_WINNT >= 0x0600)
 #define HAVE_STRUCT_POLLFD 1
 #endif