libtuntap 0.4

Enhancement:

- the oldest cmake version allowed is now 3.0
- libtuntap now compiles against musl-libc thanks to an initial work by Davide Polonio (@Polpetta on Github)
- better README
- libtuntap++ is now built by default

Breaking changes:

- the TUNTAP_GET_FD() macro has been replaced by the function tuntap_get_fd()
- the struct device is now opaque

Version 0.3

Update tuntap_set_ip() calls in regress/

Merge branch 'master' of github.com:/LaKabane/libtuntap