MSG_CMSG_CLOEXEC is a flag for recvmsg and not recv. Thus rewrite
{udp,tcp}_open to create sockets with SOCK_CLOEXEC. If SOCK_CLOEXEC is not
available, FD_CLOEXEC is set instead.

The function dvbpsi_CheckPSISection() correctly checked the TOT table, but
not the TDT table. This patch corrects this ommission.

examples/dvbinfo/udp.c: Some OS-es do not support SOL_IP and SOL_IPV6, so provide alternatives for them.

Use explicite parenthesis around ? : constructions.

- add boundary checking
- add doxygen comment
- fix some typos.
- fix L1L2MERGE macro