nf: nfnl_*_str2copy_mode() should return int

... to be able to return a negative error code for unknown modes.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
xfrm: Remove unused function __assign_addr()

Signed-off-by: Thomas Graf <tgraf@suug.ch>
nf: Remove unused function htonll()

Signed-off-by: Thomas Graf <tgraf@suug.ch>
xfrm: Remove unused variable sp_id and sa_id

Cc: Sruthi Yellamraju <ysruthi@gmail.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
src: Silence all warnings

Signed-off-by: Thomas Graf <tgraf@suug.ch>
build: Add support for travis-ci

Signed-off-by: Thomas Graf <tgraf@suug.ch>