Revert 0e4c4d6 ("Fix minor typeset attribute regressions")

This commit introduced the following bug, which is worse than the
one that commit fixed: it became impossible to alter the size of an
existing justified string attribute.

Thanks to @hyenias for catching this bug:
#142 (comment)

$ unset s; typeset -L 100 s=h; typeset +p s; typeset -L 5 s; typeset +p s
typeset -L 100 s
typeset -L 100 s

Expected output:
typeset -L 100 s
typeset -L 5 s

src/cmd/ksh93/sh/name.c:
- Revert.

src/cmd/ksh93/tests/attributes.sh:
- Revert: re-disable tests for minor attribute output regressions.
- Add a test for this bug and potential similar bugs.

src/cmd/ksh93/sh/name.c

@@ -2985,10 +2985,11 @@ void nv_newattr (register Namval_t *np, unsigned newatts, int size)
 			nv_onattr(np,NV_EXPORT);
 			sh_envput(shp->env,np);
 		}
+		if((n^newatts)==NV_EXPORT && !trans)
+			/* Only EXPORT attribute has changed and thus all work has been done. */
+			return;
 	}
 	oldsize = nv_size(np);
-	if(((n^newatts) & ~(NV_EXPORT|NV_RDONLY))==0)
-		size = oldsize;
 	if((size==oldsize|| (n&NV_INTEGER)) && !trans && ((n^newatts)&~NV_NOCHANGE)==0)
 	{
 		if(size>0)

src/cmd/ksh93/tests/attributes.sh

@@ -526,16 +526,16 @@ typeset -A expect=(
 	[F12]='typeset -x -r -F 12 foo'
 	[H]='typeset -x -r -H foo'
 	[L]='typeset -x -r -L 0 foo'
-	[L17]='typeset -x -r -L 17 foo'
+#	[L17]='typeset -x -r -L 17 foo'		# TODO: outputs '-L 0'
 	[Mtolower]='typeset -x -r -l foo'
 	[Mtoupper]='typeset -x -r -u foo'
 	[R]='typeset -x -r -R 0 foo'
-	[R17]='typeset -x -r -R 17 foo'
+#	[R17]='typeset -x -r -R 17 foo'		# TODO: outputs '-L 0'
 	[X17]='typeset -x -r -X 17 foo'
 	[S]='typeset -x -r foo'
 	[T]='typeset -x -r foo'
 	[Z]='typeset -x -r -Z 0 -R 0 foo'
-	[Z13]='typeset -x -r -Z 13 -R 13 foo'
+#	[Z13]='typeset -x -r -Z 13 -R 13 foo'	# TODO: outputs 'typeset -x -r -Z 0 -R 0 foo'
 )
 for flag in "${!expect[@]}"
 do	unset foo
@@ -614,5 +614,20 @@ do	unset a
 done
 unset expect
 
+# ======
+# https://github.com/ksh93/ksh/issues/142#issuecomment-780931533
+got=$(unset s; typeset -L 100 s=h; typeset +p s; typeset -L 5 s; typeset +p s)
+exp=$'typeset -L 100 s\ntypeset -L 5 s'
+[[ $got == "$exp" ]] || err_exit 'cannot alter size of existing justified string attribute' \
+	"expected $(printf %q "$exp"), got $(printf %q "$got")"
+got=$(unset s; typeset -L 100 s=h; typeset +p s; typeset -R 5 s; typeset +p s)
+exp=$'typeset -L 100 s\ntypeset -R 5 s'
+[[ $got == "$exp" ]] || err_exit 'cannot set -R after setting -L' \
+	"expected $(printf %q "$exp"), got $(printf %q "$got")"
+got=$(unset s; typeset -L 100 s=h; typeset +p s; typeset -Z 5 s; typeset +p s)
+exp=$'typeset -L 100 s\ntypeset -Z 5 -R 5 s'
+[[ $got == "$exp" ]] || err_exit 'cannot set -Z after setting -L' \
+	"expected $(printf %q "$exp"), got $(printf %q "$got")"
+
 # ======
 exit $((Errors<125?Errors:125))