dirstate: swap pathto() and get_entry() in idirstate

This way the order of methods in dirstate and idirstate classes is the same.
Just to make it easier to use diff tools to compare the two classes.

mercurial/interfaces/dirstate.py

@@ -67,12 +67,12 b' class idirstate(interfaceutil.Interface)'
         used to get real file paths. Use vfs functions instead.
         """
 
+    def pathto(f, cwd=None):
+        pass
+
     def get_entry(path):
         """return a DirstateItem for the associated path"""
 
-    def pathto(f, cwd=None):
-        pass
-
     def __contains__(key):
         """Check if bytestring `key` is known to the dirstate."""