Replaced nondeterministic parts of test-byte-order.cpp.

Our byte-order code is constexpr, so testing against literals in release
builds reduces to compile time evaluation. The only real ways to prevent
this reduction is to use values that can only be determined at runtime. The
original solution was to use buffers of random data. This explodes when valu
to be swapped happen to randomly match. We now construct an array at runtime
If the compiler is smart enough to reduce this, so be it.