mpatch: proxy through mdiff module

See the previous commit for why.

contrib/bdiff-torture.py

@@ -6,7 +6,6 b' import sys'
 
 from mercurial import (
     mdiff,
-    mpatch,
 )
 
 def reducetest(a, b):
@@ -45,7 +44,7 b' def test1(a, b):'
     d = mdiff.textdiff(a, b)
     if not d:
         raise ValueError("empty")
-    c = mpatch.patches(a, [d])
+    c = mdiff.patches(a, [d])
     if c != b:
         raise ValueError("bad")
 

tests/test-bdiff.py

@@ -5,7 +5,6 b' import unittest'
 
 from mercurial import (
     mdiff,
-    mpatch,
 )
 
 class diffreplace(
@@ -19,7 +18,7 b' class BdiffTests(unittest.TestCase):'
         d = mdiff.textdiff(a, b)
         c = a
         if d:
-            c = mpatch.patches(a, [d])
+            c = mdiff.patches(a, [d])
         self.assertEqual(
             c, b, ("bad diff+patch result from\n  %r to\n  "
                    "%r: \nbdiff: %r\npatched: %r" % (a, b, d, c[:200])))