fixed bug #43389 dns_recv() res_idx calculate error
fixed bug #43173, pppos_input() corrupts memory if IP_FORWARD is enabled
fixed bug #43235, cleared compiler warnings when using gcc with -Wextra option
fixed bug #43235, checking for non-existent preprocessor macros is non-standard, added predefinition for all affected macros
Merge branch 'master' of git://git.savannah.nongnu.org/lwip