redo-if*.py: import fewer things from helpers.

Just to keep track of how many helper functions we actually are using.  In
case I get brave and try to convert to C sometime.

redo-ifchange.py

@@ -1,7 +1,7 @@
 #!/usr/bin/python
 import sys, os
 import vars
-from helpers import *
+from helpers import sname, add_dep, debug, err, mkdirp, unlink
 
 
 def _dirty_deps(t, depth):

redo-ifcreate.py

@@ -1,7 +1,7 @@
 #!/usr/bin/python
 import sys, os
 import vars
-from helpers import *
+from helpers import err, add_dep, mkdirp
 
 
 if not vars.TARGET: