tipc: Add support for SO_SNDTIMEO socket option

Adds support for the SO_SNDTIMEO socket option. (This complements the
existing support for SO_RCVTIMEO that is already present.)

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>