Fixes #21 - Implement byte-order swapping routines

kt::sdk::bswap64, kt::sdk::bswap32, and kt::sdk::bswap16, each allow
the byte-order swapping of integral types.

On certain platforms (using GCC or clang), these functions will make
use of the __builtin_bswapXX routines. Additional platforms can be
added if the generated code looks good.
Merge pull request #21 from caitp/issue-21

[enhance] explicit support for byte-order conversion