Fix compile error in net.c with musl libc

fixes #278
diff --git a/library/net.c b/library/net.c
index b5d0688..a77268c 100644
--- a/library/net.c
+++ b/library/net.c
@@ -292,7 +292,7 @@
     struct sockaddr_storage client_addr;
 
 #if defined(__socklen_t_defined) || defined(_SOCKLEN_T) ||  \
-    defined(_SOCKLEN_T_DECLARED)
+    defined(_SOCKLEN_T_DECLARED) || defined(__DEFINED_socklen_t)
     socklen_t n = (socklen_t) sizeof( client_addr );
     socklen_t type_len = (socklen_t) sizeof( type );
 #else