In addition to unix domain sockets, Linux also supports an
abstract namespace which is independent of the filesystem.
In order to support it, add new CURLOPT_ABSTRACT_UNIX_SOCKET
option which uses the same storage as CURLOPT_UNIX_SOCKET_PATH
internally, along with a flag to specify abstract socket.
On non-supporting platforms, the abstract address will be
interpreted as an empty string and fail gracefully.
Also add new --abstract-unix-socket tool parameter.
Signed-off-by: Isaac Boukris <iboukris@gmail.com>
Reported-by: Chungtsun Li (typeless)
Reviewed-by: Daniel Stenberg
Reviewed-by: Peter Wu
Closes#1197Fixes#1061
