fix uintNkorr in byte_order_generic.h, avoid unaligned access

Compilers are getting (too) smart, and they can generate incorrect code, for unaligned access, since it is "undefined behavior".

Also, avoid macros, like MySQL did, it is almost impossible to read now. `static inline` is good enough, and documents correct datatype
of the return value.

• the correct optimization for all little endian is something like this.

static inline uint uint4korr(const void *p)

{

  uint ret;

  memcpy(&ret, p, 4);

  return ret;

}

It is optimized by the compiler to a single instruction, if alignment is unimportant in that architecture.
Corollary : There is no whatever reason to have special code for Intel, memcpy is the best.
We only need set of such static inline functions for big and little endian architectures, nothing more.

For big-endian, byte-wise reading and calculating are in order. That code might also by optimized by the compiler, if architecture has a byteswapping instructions.