Bump C++ standard to 17 due to inline extension

[klemensn]

.../noson/src/private/byteorder.h:57:8: warning: inline variables are a C++17 extension [-Wc++17-extensions]
static inline int16_t swap16(int16_t val)
       ^

[janbar]

That is my code from C, so a function static inline. It is not a variable. As it is included in c++ source, I have to remove static keyword.