sh: Add test for exit status of for loop without items.

POSIX says the exit status of a for loop without any items shall be 0. There
are no exceptions if the exit status of the previous command was not 0 or if
the item list contains a command substitution with non-zero exit status.

tools/regression/bin/sh/builtins/for1.0

@@ -0,0 +1,4 @@
+# $FreeBSD$
+
+false
+for i in `false`; do exit 3; done