signal: initial signal handling

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Signed-off-by: Emil Renner Berthing <esmil@mailme.dk>
signal: add signal lookup

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Signed-off-by: Emil Renner Berthing <esmil@mailme.dk>
signal: handle sigchild separately

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Signed-off-by: Emil Renner Berthing <esmil@mailme.dk>
signal: add test

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Signed-off-by: Emil Renner Berthing <esmil@mailme.dk>
signal: add support for looking up signals by number

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Signed-off-by: Emil Renner Berthing <esmil@mailme.dk>
suppress libev strict-aliasing warnings

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.biz>
Signed-off-by: Emil Renner Berthing <esmil@mailme.dk>