build: Add continuous integration support via travis-ci

This allows any libnl github repo to link to travis-ci which
will result in new commits and pull requests to be automatically
built with both gcc and clang. Any build failures including the
addition of warnings are reported to the author and committer.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Thomas Haller <thaller@redhat.com>
nf: nfnl_*_str2copy_mode() should return int

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

[thaller@redhat.com: This is potentially an ABI break, but since
the size of the enum is implementation defined, it seems
anyway unstable to have them as function arguments/return values.]

http://lists.infradead.org/pipermail/libnl/2014-August/001616.html

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

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

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

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

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Thomas Haller <thaller@redhat.com>
Merge branch 'tgraf/trivial-fixes'

http://lists.infradead.org/pipermail/libnl/2014-August/001614.html

Signed-off-by: Thomas Haller <thaller@redhat.com>