Move atoi() into atoi.py and add a new debug2() debug level.

atoi() was getting redundant, and unfortunately we can't easily load
helpers.py in some places where we'd want to, because it depends on vars.py.
So move it to its own module.

redo.py

@@ -1,6 +1,6 @@
 #!/usr/bin/python
 import sys, os, subprocess, glob, time, random
-import options, jwack
+import options, jwack, atoi
 
 optspec = """
 redo [targets...]
@@ -16,7 +16,7 @@ o = options.Options('redo', optspec)
 targets = extra or ['all']
 
 if opt.debug:
-    os.environ['REDO_DEBUG'] = '1'
+    os.environ['REDO_DEBUG'] = str(opt.debug or 0)
 if opt.verbose:
     os.environ['REDO_VERBOSE'] = '1'
 if opt.shuffle:
@@ -67,6 +67,7 @@ def _possible_do_files(t):
 
 def find_do_file(t):
     for dofile,basename,ext in _possible_do_files(t):
+        debug2('%s: %s ?\n' % (t, dofile))
         if os.path.exists(dofile):
             add_dep(t, 'm', dofile)
             return dofile,basename,ext
@@ -214,7 +215,7 @@ if not vars.DEPTH:
     os.environ['PATH'] = ':'.join(dirnames) + ':' + os.environ['PATH']
 
 try:
-    j = atoi(opt.jobs or 1)
+    j = atoi.atoi(opt.jobs or 1)
     if j < 1 or j > 1000:
         err('invalid --jobs value: %r\n' % opt.jobs)
     jwack.setup(j)