fix #1194: Regular expression catastrophic backtracking in bottle.Rou…

…ter.rule_syntax

This backports the patch from aaee93a to the 0.12 release branch.

This fix can be validated with the following command from the issue:

    python -c "import bottle; list(bottle.Router.rule_syntax.finditer('<abc:def:' + '.' * 64 + '<'))"

bottle.py

@@ -308,7 +308,7 @@ def add_filter(self, name, func):
     rule_syntax = re.compile('(\\\\*)'\
         '(?:(?::([a-zA-Z_][a-zA-Z_0-9]*)?()(?:#(.*?)#)?)'\
           '|(?:<([a-zA-Z_][a-zA-Z_0-9]*)?(?::([a-zA-Z_]*)'\
-            '(?::((?:\\\\.|[^\\\\>]+)+)?)?)?>))')
+            '(?::((?:\\\\.|[^\\\\>])+)?)?)?>))')
 
     def _itertokens(self, rule):
         offset, prefix = 0, ''