[NaCl SDK] nacl_io: Add support for basic socketpairs.

native_client_sdk/src/libraries/nacl_io/library.dsc

 {
   'TOOLS': ['newlib', 'glibc', 'bionic', 'pnacl', 'linux', 'mac', 'clang-newlib'],
   'SEARCH': [
     '.',
     'pepper',
     '../third_party/newlib-extras',
     'include',
   ],
   'TARGETS': [
     {
@@ skipping 45 matching lines @@
         "pipe/pipe_event_emitter.cc",
         "pipe/pipe_node.cc",
         "real_pepper_interface.cc",
         "socket/fifo_packet.cc",
         "socket/packet.cc",
         "socket/socket_node.cc",
         "socket/tcp_event_emitter.cc",
         "socket/tcp_node.cc",
         "socket/udp_event_emitter.cc",
         "socket/udp_node.cc",
+        "socket/unixsocket_event_emitter.cc",
+        "socket/unixsocket_node.cc",
         "stream/stream_event_emitter.cc",
         "stream/stream_fs.cc",
         "stream/stream_node.cc",
         "syscalls/access.c",
         "syscalls/chown.c",
         "syscalls/fchown.c",
         "syscalls/fcntl.c",
         "syscalls/ftruncate.c",
         "syscalls/futimes.c",
         "syscalls/getwd.c",
@@ skipping 127 matching lines @@
         "pipe/pipe_event_emitter.h",
         "pipe/pipe_node.h",
         "real_pepper_interface.h",
         "socket/fifo_packet.h",
         "socket/packet.h",
         "socket/socket_node.h",
         "socket/tcp_event_emitter.h",
         "socket/tcp_node.h",
         "socket/udp_event_emitter.h",
         "socket/udp_node.h",
+        "socket/unixsocket_event_emitter.h",
+        "socket/unixsocket_node.h",
         "stream/stream_event_emitter.h",
         "stream/stream_fs.h",
         "stream/stream_node.h",
         "typed_fs_factory.h",
       ],
       'DEST': 'include/nacl_io',
     },
     {
       'FILES': [
         "arpa/inet.h",
@@ skipping 62 matching lines @@
         "all_interfaces.h",
         "define_empty_macros.h",
         "undef_macros.h",
       ],
       'DEST': 'include/nacl_io/pepper',
     }
   ],
   'DEST': 'src',
   'NAME': 'nacl_io',
 }