The former was deprecated with C++14.

According to the C++11 and C++17 standards, both files are identical.
Signed-off-by: Rosen Penev <rosenp@gmail.com>

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

The implicit cast operator can be very dangerous.

Fixes build failure because Bionic doesn't provide SUN_LEN().

For improved portability of the net library to projects without
autoconf.