util: remove the copypasta unquote function

util: remove the copypasta unquote function

The _urlunquote function was added back in the day to improve startup
performance, but this version is a) not compatible with Python 3 and b) has
quadratic performance issues that Python core solved eons ago.

Moreover, the function moved from urllib to urlparse (cheaper to import) *and*
that module is already imported into pycompat. As a result, removing this
function improves perf now.

Before:

! wall 0.066773 comb 0.000000 user 0.000000 sys 0.000000 (best of 100)

After:

! wall 0.065990 comb 0.000000 user 0.000000 sys 0.000000 (best of 100)

--- a/mercurial/util.py	Fri Oct 07 08:51:50 2016 -0700
+++ b/mercurial/util.py	Fri Oct 07 17:06:55 2016 +0200
@@ -2301,26 +2301,6 @@
 _hextochr = dict((a + b, chr(int(a + b, 16)))
                  for a in string.hexdigits for b in string.hexdigits)
 
-def _urlunquote(s):
-    """Decode HTTP/HTML % encoding.
-
-    >>> _urlunquote('abc%20def')
-    'abc def'
-    """
-    res = s.split('%')
-    # fastpath
-    if len(res) == 1:
-        return s
-    s = res[0]
-    for item in res[1:]:
-        try:
-            s += _hextochr[item[:2]] + item[2:]
-        except KeyError:
-            s += '%' + item
-        except UnicodeDecodeError:
-            s += unichr(int(item[:2], 16)) + item[2:]
-    return s
-
 class url(object):
     r"""Reliable URL parser.
 
@@ -2489,7 +2469,7 @@
                   'path', 'fragment'):
             v = getattr(self, a)
             if v is not None:
-                setattr(self, a, _urlunquote(v))
+                setattr(self, a, pycompat.urlparse.unquote(v))
 
     def __repr__(self):
         attrs = []