fix #1155: Catastrophic backtracking issue in template parser.

Related to #1194

This backports the patch from 332215b to the 0.12 release branch.

This fix can be validated using the following repl commands:

    >>> import bottle
    >>> bottle.template("""<img src="{{usar_webp(''/static/images/branco400.jpg')}}" alt="Sem imagem"/>""")

bottle.py

@@ -3489,7 +3489,7 @@ class StplParser(object):
     # Match the start tokens of code areas in a template
     _re_split = '(?m)^[ \t]*(\\\\?)((%(line_start)s)|(%(block_start)s))(%%?)'
     # Match inline statements (may contain python strings)
-    _re_inl = '(?m)%%(inline_start)s((?:%s|[^\'"\n]*?)+)%%(inline_end)s' % _re_inl
+    _re_inl = '(?m)%%(inline_start)s((?:%s|[^\'"\n])*?)%%(inline_end)s' % _re_inl
     _re_tok = '(?m)' + _re_tok
 
     default_syntax = '<% %> % {{ }}'