Fix CATCH/CONTROL phaser and thread interaction.

We over-shared the blocks, meaning that once threads showed up we got
into weird problems. Possibly recursion could reproduce it too. In the
threads case, the CATCH in Lock.protect sometimes tried to unlock the
wrong mutex.

src/Perl6/Actions.nqp

@@ -6573,11 +6573,20 @@ class Perl6::Actions is HLL::Actions does STDActions {
                 QAST::Var.new( :name($exceptionreg), :scope('local') )));
         }
 
-        # create code that calls our handler with the Parrot exception
-        # as argument and returns the result. The install the handler.
+        # Install the handler, taking care over scoping.
+        my $handler_lex_name := $handler.unique('__HANDLER_');
+        $*W.cur_lexpad()[0].push(QAST::Op.new(
+            :op('bind'),
+            QAST::Var.new( :name($handler_lex_name), :scope('lexical'), :decl('var') ),
+            block_closure($handler)
+        ));
         %*HANDLERS{$type} := QAST::Stmts.new(
             :node($/),
-            QAST::Op.new( :op('p6invokehandler'), $handler, $ex ),
+            QAST::Op.new(
+                :op('p6invokehandler'),
+                QAST::Var.new( :name($handler_lex_name), :scope('lexical') ),
+                $ex
+            ),
             QAST::Var.new( :scope('lexical'), :name('Nil') )
         );
     }