nghttpx: Only use thread_local if NOTHREADS is not defined
Disable threading for android build because it lacks thread local storage
nghttpx: Use 431 instead of 413
src: Add additional HTTP status codes defined in RFC 6585
doc: Generate HTML version manual page from manpage
Send additional debug info when terminating session
Check NGHTTP2_GOAWAY_SEND and NGHTTP2_GOAWAY_RECV flags explicitly
nghttpd: Don't shutdown session if pending data is left
nghttpx: Log transmission and reception of GOAWAY
Handle multiple SETTINGS_HEADER_TABLE_SIZE in incoming SETTINGS frame

Previously we just assumed that if same settings ID is found in
SETTINGS, it is enough to process last seen entry.  But it turns out
it is not enough for SETTINGS_HEADER_TABLE_SIZE.  If we have 0 and
4096 for SETTINGS_HEADER_TABLE_SIZE in one SETTINGS, we must first
shrink dynamic table to 0 and then enlarge it to 4096.  This means
that we have to remember the minimum value and last value.
Fix double free
src: Retry write(2) if errno == EINTR
Remove unused nghttp2_io_flag
examples: Fix possible division by zero
Fix resource leaks
Remove unused nghttp2_nva_out
Update README.rst
Bump up version number to 0.5.0, LT revision to 4:0:0
Update man pages
Bump up version number to 0.5.1-DEV