match: use util.re.escape instead of re.escape

For a pathological .hgignore with over 2500 glob lines and over 200000 calls to
re.escape, and with re2 available, this speeds up parsing the .hgignore from
0.75 seconds to 0.20 seconds. This causes e.g. 'hg status' with hgwatchman
enabled to go from 1.02 seconds to 0.47 seconds.

mercurial/match.py

@@ -247,7 +247,7 b' def _globre(pat):'
     i, n = 0, len(pat)
     res = ''
     group = 0
-    escape = re.escape
+    escape = util.re.escape
     def peek():
         return i < n and pat[i]
     while i < n:
@@ -310,11 +310,11 b' def _regex(kind, pat, globsuffix):'
     if kind == 're':
         return pat
     if kind == 'path':
-        return '^' + re.escape(pat) + '(?:/|$)'
+        return '^' + util.re.escape(pat) + '(?:/|$)'
     if kind == 'relglob':
         return '(?:|.*/)' + _globre(pat) + globsuffix
     if kind == 'relpath':
-        return re.escape(pat) + '(?:/|$)'
+        return util.re.escape(pat) + '(?:/|$)'
     if kind == 'relre':
         if pat.startswith('^'):
             return pat