Log Message:
Update to version 9.21.

Changes:

- the "moa redraw 8-bit british vintage colour management" release.
- NOTICE: this release updates terminfo.
- fix pixel droppings on overdraw when a secondary core font has the
  same height but different ascent.
- implement cvvis in terminfo as blinking cursor, to distinguish it
  from cnorm (emacs uses cvvis which is commonly a blinking cursor).
- when xft support was compiled in, colour queries erroneously returned
  premultiplied values, this also affected internal queries, for example
  when calculating faded colour. alpha is now divided out when possible,
  which is more correct but loses colour resolution.
- add DECSCUSR xterm extension to set the cursor to a vertical bar.
- add 'extension:string' action, and associated on_action perl
  hook, for keysym resources that invokes actions provided by
  perl extensions. The 'perl:string' action and
  on_user_command hook are deprecated but still supported.
- add 'builtin-string' action for keysym resources that restores string
  mappings for keys that have predefined actions in urxvt.
- add -k option to urxvtc for killing the daemon process.
- document urxvtd's -e/--eval option that was implemented in 9.16,
  but not documented.
- add -dockapp option to make the wm treat urxvt as a dockapp.
- add -mc option and multiClickTime resource to set the maximum time
  between multi-click select events (patch by Joe Peterson).
- new 'eval' extension to evaluate arbitrary perl code with keysym
  bindings. The extension also provides methods that implement basic
  actions, such as pasting selections and scrolling.
- the macosx-clipboard and macosx-clipboard-native extensions have been removed.
- kuake extension now uses the kuake.hotkey resource to specify the hotkey.
- new 'matcher:select' mode of matcher to iterate over the matches with the keyboard.
- the 'matcher:list' feature of matcher now honours the launcher
  associated to a matched pattern.
- speed-up matcher underlining on very long lines (reported by Edward Z. Yang).
- fix up/down commands of searchable-scrollback so that they always move
  to the previous/next logical line with a match, if any.
- searchable-scrollback resource has been deprecated (use keysym instead).
- extension parameter passing is deprecated (use resource mechanism instead).
- upgrade to GPLv3 (see COPYING).
- compile out of the box on Solaris 10, again.
- fix height and position of the stippled area in next scrollbar (patch
  by Thomas Otto).
- fix off-by-one bug causing the iso14755 window not to jump out of the
  way properly.
- fix crash that may happen if a lib to which urxvt is linked to calls setenv.
- fix memory leak in special_{encode,decode} perl methods.
- fix refresh bug that occurs when reverse video is set on a cell
  containing a space and with the same bg and fg colour, red hat bug
  #830236.
- fix crash that may happen if an x error is received after a terminal
  window/popup has been destroyed already.
- removed superfluous 0 digit from sgr terminfo sequence.
- greatly improve colour allocation on colour-starved pseudocolour
  displays to avoid read-write cells instead of simply failing
  (this is only relevant for antique 8bpp frame buffers).
- do not free fade colours when not doing fading (this is likely
  only relevant for antique 8bpp frame buffers).
- do not specialcase 2 or 4 colour visuals, leading to
  simpler and actually more correct code.
- hopefully no longer leak colours on !truecolour visuals.
- use consistent method names (scr_recolour => scr_recolor).
- use simpler (but slightly less bogus) formula for nearest
  colour choice (this is likely only relevant for antique 8bpp
  frame buffers).
- remove fallback behaviour when initialising colours - the
  behaviour was inconsistent between startup vs. later and
  was only effective when valid colours couldn't be allocated.