Define `_XPG4_2` on SunOS

This brings `strcasecmp`.
Disable stack smashing protection

Even despite linking with `-lssp`, building with stack smashing
protection on SmartOS causes:

    Undefined                       first referenced
     symbol                             in file
    __stack_chk_fail_local              build_sunos/crypto_AddressCalc_c.o  (symbol scope specifies local binding)
    ld: fatal: symbol referencing errors. No output written to ./privatetopublic