* remove wrapped buffer read/write support on platforms without

* remove wrapped buffer read/write support on platforms without
readv/writev  (buf.c)

* add buf_removed() and buf_added() (buf.c)

* rewrite do_work(): breaking the npipe and socket handling into their own
  routines (mod_fastcgi.c and buf.c)

* use async/overlapped io instead of non-blocking npipes - this eliminates
the use of (broken) polling (mod_fastcgi.c)

* require Apache version >= 1.3.6 to elminate the need for the funky
signal handling (mod_fastcgi.c)

* properly dispose of stdin received in redirects (protocol.c)