strutil: use absolute_import

This file doesn't import anything. But chances are we'll eventually
implement a static analysis check that ensures absolute_import is used.
So we might as well add this.

mercurial/strutil.py

@@ -1,34 +1,36 b''
 # strutil.py - string utilities for Mercurial
 #
 # Copyright 2006 Vadim Gelfer <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+from __future__ import absolute_import
+
 def findall(haystack, needle, start=0, end=None):
     if end is None:
         end = len(haystack)
     if end < 0:
         end += len(haystack)
     if start < 0:
         start += len(haystack)
     while start < end:
         c = haystack.find(needle, start, end)
         if c == -1:
             break
         yield c
         start = c + 1
 
 def rfindall(haystack, needle, start=0, end=None):
     if end is None:
         end = len(haystack)
     if end < 0:
         end += len(haystack)
     if start < 0:
         start += len(haystack)
     while end >= 0:
         c = haystack.rfind(needle, start, end)
         if c == -1:
             break
         yield c
         end = c - 1