In FreeBSD conditional inclusion of constexpr specifier causes error
In FreeBSD conditional inclusion of constexpr specifier causes error

So remove constexpr specifiers from EXT_SPORT, EXT_DPORT, EXT_SIP,
EXT_DIP functions. Anyway current use cases don't need compile time
detemination of function result (at least one argument is run time
determined)

petabi/regexbench,petabi/regexbench,petabi/regexbench,petabi/regexbench