Support ksh alternative names (#2697)

* Support ksh versions

Korn shell had two major versions: ’88 and ’93. Some systems have
ksh installed under the name `ksh93`. A few systems (maybe only
Solaris now) also have a `ksh88`. A few others use the `pdksh` (’88)
or `mksh` (’93) implementations, originated before ksh was open source.

Limit to currently-used versions

---------

Co-authored-by: Kevin Schoedel <kps@datatravelandexperiments.com>

libexec/pyenv-init

@@ -109,7 +109,12 @@ function detect_profile() {
     profile='~/.zprofile'
     rc='~/.zshrc'
     ;;
-  ksh )
+  ksh | ksh93 | mksh )
+    # There are two implementations of Korn shell: AT&T (ksh93) and Mir (mksh).
+    # Systems may have them installed under those names, or as ksh, so those
+    # are recognized here. The obsolete ksh88 (subsumed by ksh93) and pdksh
+    # (subsumed by mksh) are not included, since they are unlikely to still
+    # be in use as interactive shells anywhere.
     profile='~/.profile'
     rc='~/.profile'
     ;;
@@ -269,7 +274,7 @@ function pyenv
 end
 EOS
     ;;
-  ksh )
+  ksh | ksh93 | mksh )
     cat <<EOS
 function pyenv {
   typeset command