utils: rename files and internals (add 'k' prefix)

src/Makefile.am

src/utils/common/hex.c

src/utils/common/netio.c

src/utils/common/resolv.c

src/utils/common/strtonum.h

src/utils/common/token.c

src/utils/kdig/kdig_exec.c

src/utils/kdig/kdig_exec.h

src/utils/kdig/kdig_main.c

src/utils/kdig/kdig_params.c

src/utils/kdig/kdig_params.h

src/utils/khost/khost_main.c

src/utils/khost/khost_params.c

src/utils/khost/khost_params.h

src/utils/knsec3hash/knsec3hash_main.c

src/utils/knsupdate/KNOWN_ISSUES

src/utils/knsupdate/knsupdate_exec.c

src/utils/knsupdate/knsupdate_exec.h

src/utils/knsupdate/knsupdate_main.c

src/utils/knsupdate/knsupdate_params.c