move private header file to src

[Damien-Chen]

Move "twin_private.h" to src folder, and make a new "util.h" header file that include necessary header file for the expansion of future use.

[jserv]

The header twin_private.h is used internally, and don't create any header referring to it. See #9

[Damien-Chen]

Based on my understanding, so we can directory include twin_private.h in source code, but indirectory include is no need right ? (based on my change, I create util.h include twin_private.h)

[jserv]

Based on my understanding, so we can directory include twin_private.h in source code, but indirectory include is no need right ?

The include directory should contain twin.h as the public header and nothing more, meaning that the current twin_private.h is a hack to allow the building of some applications invoking the internal functions. You can proceed with issue #9 to contribute to this project.

[jserv]

Close to concentrate on #9