TODO
----

o Perhaps move 1024-buffer of writef into sa_t and make adjustable or
  even better: provide a sa_mvsnprintf() variant which directly does the
  sa_write calls and this way the whole buffering is the SA_BUFFER_WRITE.
  This would be exactly what the user would expect.

o Provide a full test suite for the whole API.

  - inet://0.0.0.0:0 -> inet://0.0.0.0:514
  - inet://127.0.0.1:514 -> inet://127.0.0.1:514
  - inet://localhost:syslog#udp -> inet://127.0.0.1:514
  - inet://localhost:smtp -> inet://127.0.0.1:25
  - unix:/tmp/socket -> unix:/tmp/socket

o Use sa_errorinfo() internally everywhere where it is reasonable.

CANDO
-----

o Support for writev(2).

  This can be done by internally switching to always use writev(2),
  providing an emulation for writev(2) ala Pth and by basing the write
  calls always on writev.
  
o Kernel Read/Write Buffer Adjustments.

  BSD Sockets usually provide (see setsockopt(2)):

      SO_SNDBUF          set buffer size for output
      SO_RCVBUF          set buffer size for input
      SO_SNDLOWAT        set minimum count for output
      SO_RCVLOWAT        set minimum count for input

  This would mean that we could also allow the control
  of the kernel buffers via

      SA_BUFFER_KREAD
      SA_BUFFER_KWRITE

  Unfortunately the whole kernel buffer issue is very complex, because
  according to STEVENS there are both minimum and maximum sizes and both
  borders heavily depend on the currently used protocol (TCP or UDP) and
  the MTU of the underlying network, etc. This all together seems like
  opening a can of worms if we provide SA_BUFFER_K{READ,WRITE}.