ash: [EVAL] Make eval with empty arguments return 0

This is a backport of upstream commit:

    [EVAL] Make eval with empty arguments return 0

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/ash_test/ash-misc/eval1.tests b/shell/ash_test/ash-misc/eval1.tests
new file mode 100755
index 0000000..b78c6cc
--- /dev/null
+++ b/shell/ash_test/ash-misc/eval1.tests
@@ -0,0 +1,4 @@
+# empty eval nevertheless sets $? = 0
+false
+eval
+echo Ok:$?