undef ip_len to avoid naming conflict between struct ip from <netinet/ip.h>
and local variable ip_len defined in this file

diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -82,6 +82,13 @@
 
 #include "debug_sync.h"
 
+// AIX defines the ip_len field in struct ip's to be a macro of an inner struct,
+// but this definition conflicts with the ip_len variable defined in this file
+// We undefine the macro, since we don't use the structure or field here
+#ifdef ip_len
+#undef ip_len
+#endif
+
 #ifndef EMBEDDED_LIBRARY
 static bool delayed_get_table(THD *thd, MDL_request *grl_protection_request,
                               TABLE_LIST *table_list);