Issue #23735: Merge Readline resize handling from 3.5

diff --cc Misc/ACKS
Simple merge

diff --cc Misc/NEWS
index f66014a7dc921382fc6076d7188baf8339c05646,6d43666b56d94446b621d685a43050712c197fc7..8cd2339f953038fcfc687285fdd001d9702fa1d4
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -237,9 -98,10 +237,12 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #23735: Handle terminal resizing with Readline 6.3+ by installing our
+   own SIGWINCH handler.  Patch by Eric Price.
+ 
 +- Issue #25951: Change SSLSocket.sendall() to return None, as explicitly
 +  documented for plain socket objects.  Patch by Aviv Palivoda.
 +
  - Issue #26586: In http.server, respond with "413 Request header fields too
    large" if there are too many header fields to parse, rather than killing
    the connection and raising an unhandled exception.  Patch by Xiang Zhang.

diff --cc Modules/readline.c
Simple merge

diff --cc configure
Simple merge

diff --cc configure.ac
Simple merge