Add two fundamental tests for copying directories

testsuite/cp/cp-dir-create-dir

@@ -0,0 +1,4 @@
+mkdir bar 
+touch bar/baz
+busybox cp -R bar foo 
+test -f foo/baz 

testsuite/cp/cp-dir-existing-dir

@@ -0,0 +1,5 @@
+mkdir bar 
+touch bar/baz
+mkdir foo
+busybox cp -R bar foo 
+test -f foo/bar/baz