Enable path validation for copy, rename, debugwalk and other canonpath users. This fixed the last bit of issue134. Added some tests to test-rename and test-walk.

#!/bin/sh

hg init
echo This is file a1 > a
hg add a
hg commit -m "commit #0" -d "1000000 0"
touch b
hg add b
rm b
hg commit -A -m"comment #1" -d "1000000 0"