NEWS/README: Add missing change documentation for 5.9

This covers the following changes:

users/24971: ${(-)var} sorts on signed integers

47704: POSIX export and readonly ignore "-p" when parameter names also appear

47913: implement CASE_PATHS option to make NO_CASE_GLOB more sensible

48073: Add fc -s as POSIX way of rerunning command without starting editor

49307 with doc update: POSIX_TRAPS fix.

49528: allow multiple -D options to compadd

49534, 49539: separate watch/log functionality out into a module

49561: add zformat -F option, similar to -f but ternary expressions check for
existence instead of doing math evaluation

49597: add a helper for completing numbers with unit suffixes and separate out
defaults, ranges and units in completion descriptions

49611 based on 49590 (Martijn Dekker): disable Inf and NaN in math expressions
for sh emulation

49646: allow colors in WATCHFMT with %F/%K

49694 + doc: Allow using empty STTY= to freeze tty for a single command

49853 + 49882/49883: make "${arr[*]:off}" compatible with ksh/bash

1 files changed, 24 insertions, 9 deletions

diff --git a/README b/README
index c27d6881a..21142e17c 100644
--- a/README
+++ b/README
@@ -5,11 +5,12 @@ THE Z SHELL (ZSH)
 Version
 -------
 
-This is version 5.8.1 of the shell.  This is a security and bugfix release.
+This is version 5.9 of the shell.  This is a security and feature release.
+There are several visible improvements since 5.8.1, as well as bug fixes.
 All zsh installations are encouraged to upgrade as soon as possible.
 
 Note in particular the changes highlighted under "Incompatibilities since
-5.8" below.  See NEWS for more information.
+5.8.1" below.  See NEWS for more information.
 
 Installing Zsh
 --------------
@@ -30,16 +31,13 @@ Zsh is a shell with lots of features.  For a list of some of these, see the
 file FEATURES, and for the latest changes see NEWS.  For more
 details, see the documentation.
 
-Incompatibilities since 5.8
----------------------------
+Incompatibilities since 5.8.1
+-----------------------------
 
 compinit: A "y" response to the "Ignore ... and continue?" prompt removes
 insecure elements from the set of completion functions, where previously
 it ignored the compaudit result and included all elements.
 
-PROMPT_SUBST expansion is no longer performed on arguments to prompt-
-expansion sequences such as %F.
-
 Build-time change: The default value of the --enable-gdbm configure
 argument has changed from "yes" to "no".  Thus, the zsh/db/gdbm module will
 not be built unless --enable-gdbm is passed explicitly.
@@ -105,11 +103,25 @@ emulate sh: When zsh emulates sh, the final command in a pipeline is now run in
 a subshell.  This differs from the behavior in the native (zsh) mode, but is
 consistent with most other sh implementations.
 
+The export and readonly builtins now ignore the -p option when there are
+operands given and POSIX_BUILTINS is enabled. This more closely matches the
+behaviour of bash and ksh.
+
 getopts now calculates OPTIND in a similar manner to other shells when the
 POSIX_BUILTINS option is enabled.
 
-Incompatibilities between 5.7.1 and 5.8
----------------------------------------
+Ignored-signal traps are now inherited by subshells when the POSIX_TRAPS
+option is enabled.
+
+emulate sh: Inf and NaN are now treated as parameter names in arithmetic
+context when zsh is emulating sh.
+
+The ${name:offset:length} expansion syntax now behaves more similarly to
+other shells in that the offset and length are applied as array indices
+prior to scalar conversion in e.g. "${*:0:2}".
+
+Incompatibilities between 5.7.1 and 5.8.1
+-----------------------------------------
 
 The history expansion !:1:t2 used to be interpreted such that the 2
 was a separate character added after the history expansion.  Now
@@ -140,6 +152,9 @@ changes made in the course of fixing CVE-2019-20044.  Please report this
 to the zsh-workers mailing list if your system is affected.  See NEWS for
 more.
 
+PROMPT_SUBST expansion is no longer performed on arguments to prompt-
+expansion sequences such as %F.
+
 Incompatibilities between 5.6.2 and 5.7.1
 -----------------------------------------