0.30:
  add compiletimeassert.h
  add haveuint128.h
  byte.h now defines UNALIGNED_ACCESS_OK on x86
  add scan_ulongn, scan_8longn, scan_xlongn, scan_longn, scan_netstring
  change buffer to have a destructor function pointer
  SECURITY: fmt_strn would write one byte too many (returned right length though, so usually not a problem as that byte would be overwritten with \0 by the caller anyway)
  fmt_pad and fmt_fill fail more gracefully when srclen > maxlen
  You can now say $ make WERROR=-Werror (compiling t.c may fail but that's strictly speaking not part of the library)
  scan_html now decodes HTML entities based on the actual w3c list (from entities.json, say gmake update to fetch the current version)    added fmt_escapechar* to fmt.h (implement various escaping mechanisms also found in textcode but for a single char not a whole string, and they always escape, not just when they think it's needed)                                                                           scan_ushort was supposed to abort early and return 5 when attempting to parse "65536", because the result does not fit.  It did not.  Now it does.                                                                                                                             scan_*long, scan_*int, scan_*short now properly abort if the number would not fit
  SECURITY: check for integer overflow in stralloc_ready
  switch io_fds from array to newly implemented (hopefully thread-safe) iarray
  switch epoll from level triggering to edge triggering
  introduce io_eagain_read and io_eagain_write (discontinue using io_eagain plz)
  fix buffer_get
  add fmt_html_tagarg, fmt_xml, scan_html_tagarg
  add socket_fastopen, socket_fastopen_connect4, socket_fastopen_connect6 and socket_quickack
  on Linux, in iob_send, if MSG_MORE is defined, and the request type
    lends itself to it, used sendto/sendmsg with MSG_MORE instead of
    TCP_CORK (saves two syscalls)
  add io_fd_flags so the caller can tell io_fd whether the socket is blocking
    (saves one fcntl syscall)
  more constness for stralloc and buffer
  mmap_read/mmap_shared on zero length files no longer fail but return a
    zero length buffer
  if SOCK_NONBLOCK is defined, use it instead of socket+fcntl
  ... but if errno==EINVAL still fall back to socket+fcntl (Robert Henney)
  SECURITY: fix botched integer overflow handling logic in stralloc_ready (Giorgio)
  add critbit