tcl8: re-add tcl 8 to support building expect

I'd be happy to remove expect from core as it has been unmaintained for years,
but sadly gcc/binutils test suites are basically written in it (via dejagnu),
and ltp makes use of it as well.

I attempted porting expect to tcl 9, but it's a tcl extension and makes
extensive use of features that have been deprecated in tcl 8 and removed
in tcl 9, and even pokes into tcl internals.

At some point hopefully the GNU toolchain upstreams are going to notice;
for now we'll carry tcl (latest) and tcl8 recipes.

tcl and tcl8 packages can be co-installed, the latter is adjusted
to contain tclsh8.

tcl-dev and tcl8-dev packages can also be co-installed, a few files
in tcl8-dev are renamed to avoid clashes with tcl-dev (tcl.pc -> tcl8.pc,
and similar for tclConfig.sh and tclooConfig.sh).

(From OE-Core rev: 8ec7bfc6644aff011545dfb0f5a415e79d7b0844)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/tcltk8/tcl8/interp.patch

@@ -0,0 +1,40 @@
+From 426aa2ff62dda77fd011e8f630b9d4ea17984817 Mon Sep 17 00:00:00 2001
+From: Ross Burton <ross.burton@arm.com>
+Date: Mon, 12 Jul 2021 14:50:13 +0100
+Subject: [PATCH] tcl: fix race in interp.test
+
+The interp-36.7 patch has race conditions and is missing cleanup.  This patch by
+a Tcl maintainer should improve matters.
+
+Upstream-Status: Pending
+Signed-off-by: Ross Burton <ross.burton@arm.com>
+---
+ tests/interp.test | 7 ++++---
+ 1 file changed, 4 insertions(+), 3 deletions(-)
+
+diff --git a/tests/interp.test b/tests/interp.test
+index d742484..fc90990 100644
+--- a/tests/interp.test
++++ b/tests/interp.test
+@@ -3595,17 +3595,18 @@ test interp-36.7 {ChildBgerror sets error handler of child [1999035]} -setup {
+         variable result
+         set result [lindex $args 0]
+     }
++    set tout [after 5000 {set result timeout}]
+ } -body {
+     child eval {
+         variable done {}
+         after 0 error foo
+-        after 10 [list ::set [namespace which -variable done] {}]
+-        vwait [namespace which -variable done]
+     }
++    vwait result
+     set result
+ } -cleanup {
++    after cancel $tout
+     variable result {}
+-    unset -nocomplain result
++    unset -nocomplain result tout
+     interp delete child
+ } -result foo
+