ash: fix error during recursive processing of here document

Save the value of the checkkwd flag to prevent it being clobbered
during recursion.

Based on commit ec2c84d from git://git.kernel.org/pub/scm/utils/dash/dash.git
by Herbert Xu.

function                                             old     new   delta
readtoken                                            190     203     +13
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 13/0)               Total: 13 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash.c

@@ -11899,6 +11899,7 @@ static int
 readtoken(void)
 {
 	int t;
+	int kwd = checkkwd;
 #if DEBUG
 	smallint alreadyseen = tokpushback;
 #endif
@@ -11912,7 +11913,7 @@ readtoken(void)
 	/*
 	 * eat newlines
 	 */
-	if (checkkwd & CHKNL) {
+	if (kwd & CHKNL) {
 		while (t == TNL) {
 			parseheredoc();
 			t = xxreadtoken();
@@ -11926,7 +11927,7 @@ readtoken(void)
 	/*
 	 * check for keywords
 	 */
-	if (checkkwd & CHKKWD) {
+	if (kwd & CHKKWD) {
 		const char *const *pp;
 
 		pp = findkwd(wordtext);

shell/ash_test/ash-heredoc/heredoc3.right

@@ -0,0 +1 @@
+hello

shell/ash_test/ash-heredoc/heredoc3.tests

@@ -0,0 +1,9 @@
+echo hello >greeting
+cat <<EOF &&
+$(cat greeting)
+EOF
+{
+	echo $?
+	cat greeting
+} >/dev/null
+rm greeting