posix mode changes for interp 1150; fix for varassign redirection; fix for nameref in ${param=value} expansion

tests/nameref.right

@@ -92,6 +92,10 @@ expect <one>
 one
 expect <four>
 four
+expect <X>
+X
+expect <X>
+X
 errors = 0
 1
 2

tests/nameref4.sub

@@ -228,6 +228,20 @@ echo "expect <four>"
 echo $qux
 ckval qux ${bar[3]}
 
+bar=()
+declare -n ref='bar[1]'
+
+echo "expect <X>"
+echo ${ref=X}
+ckval ref ${bar[1]}
+
+unset -n ref
+declare -n ref
+
+echo "expect <X>"
+echo ${ref=X}
+ckval ref ${ref}
+
 # Need to add code and tests for `for' loop nameref variables
 
 echo errors = $errors