lwip/src/netif/ppp/mppe.c: In function `mppe_rekey': lwip/src/netif/ppp/mppe.c:74:15: error: declaration of`sha1' shadows a global declaration [-Werror=shadow] lwip/src/include/netif/ppp/polarssl/sha1.h:88:6: error: shadowed declaration is here [-Werror=shadow]