WL#13534: Update bundled libedit to 20190324-3.1

Update bundled libedit in MySQL to 20190324-3.1.

Current version is some years old. 

There is a number of bugs fixed by this upgrade:
 20770875, 22332089, 22930525, 24432325, 27433491, 27285445 and 28939380.

See below for full report on this bugs.

Wanted version is found here:
 https://thrysoee.dk/editline/

Download:
 https://thrysoee.dk/editline/libedit-20190324-3.1.tar.gz

FR.1: Work as before.

Fr.2: The history should be backwards compatible with the previous history file.

=========================================

Bugs effected by this WL:

 Bug#20770875 MISSING READLINE FEATURES WHEN BUILDING WITH EXTERNAL LIBEDIT 
LIBRARY
  Status: fix verified

 Bug#22332089 OFF BY ONE BUG IN LIBEDITLINE
  Status: ASAN and UBSAN testing done without any issues found

 Bug#22930525 MYSQL CLIENT CRASHES AFTER EDITING
  Status: fix verified

 Bug#24432325 CTRL-W IS BROKEN IN CLIENT
  Status: works as described here: https://www.mankier.com/7/editline
         when
          $ cat ~/.editrc
          mysql:bind -v
         is used.

 Bug#27433491 SEGMENTATION FAULT IF MULTIBYTE CHARACTER USED IN PROMPT STRING
  Status: fix verified

 Bug#27285445 CONTRIBUTION: OPENBSD BUILD FIX
  Status: fix verified by code inspection

 Bug#28939380 MYSQL CLIENT CRASHES IN LIBEDIT/TERMINAL.C
  Status: fix verified by code inspection

 BUG#89797 Memory Leak
 BUG#89798 Memory Leak
  https://bugs.mysql.com/bug.php?id=89797
  https://bugs.mysql.com/bug.php?id=89798
  Status: fixed, problematic code removed

Install the complete tarball (except some binaries which seem to be irrelevant)

Look at .am and .ac files in the bundle, and implement similar build
functionality in cmake.

Look at mysql patches to the old libedit library. These are tagged with XXXMYSQL. 
Most of these patches are now irrelevant: adaptations to platforms no longer
supported, or things which have been fixed upstream.

The only mysql patch which seems to be relevant is
    Bug#11757855 49967: BUILT-IN LIBEDIT DOESN'T READ .EDITRC ON LINUX

The new libedit library does have configure code, and C macros to use 
secure_getenv() if it is available, but the actual code in src/el.c does not use
it. So we do something similar to the patch for Bug#11757855 49967, and fall back
to using getuid() geteuid() getgid() getegid() instead of issetugid()