libfdt: More tests of NOP handling behaviour

In light of the recently discovered bug with NOP handling, this adds
some more testcases for NOP handling.  Specifically, it adds a helper
program which will add a NOP tag after every existing tag in a dtb,
and runs the standard battery of tests over trees mangled in this way.

For now, this does not add a NOP at the very beginning of the
structure block.  This causes problems for libfdt at present, because
we assume in many places that the root node's BEGIN_NODE tag is at
offset 0.  I'm still contemplating what to do about this (with one
option being simply to declare such dtbs invalid).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

tests/run_tests.sh

@@ -125,6 +125,13 @@ libfdt_tests () {
     tree1_tests rw_tree1.test.dtb
     tree1_tests_rw rw_tree1.test.dtb
 
+    for basetree in test_tree1.dtb sw_tree1.test.dtb rw_tree1.test.dtb; do
+	run_test nopulate $basetree
+	run_test dtbs_equal_ordered $basetree noppy.$basetree
+	tree1_tests noppy.$basetree
+	tree1_tests_rw noppy.$basetree
+    done
+
     # Tests for behaviour on various sorts of corrupted trees
     run_test truncated_property