Use Mustermann internally for building prefixed_path as RegexpBased pattern

Removed `regexpify` from internal API.

sinatra-contrib/lib/sinatra/namespace.rb

@@ -201,7 +201,7 @@ module Sinatra
       end
 
       def error(*codes, &block)
-        args  = Sinatra::Base.send(:compile!, "ERROR", regexpify(@pattern), block)
+        args  = Sinatra::Base.send(:compile!, "ERROR", @pattern, block)
         codes = codes.map { |c| Array(c) }.flatten
         codes << Exception if codes.empty?
 
@@ -266,16 +266,7 @@ module Sinatra
 
       def prefixed_path(a, b)
         return a || b || // unless a and b
-        a, b = regexpify(a), regexpify(b) unless a.class == b.class
-        path = a.class.new "#{a}#{b}"
-        path = /^#{path}$/ if path.is_a? Regexp and base == app
-        path
-      end
-
-      def regexpify(pattern)
-        pattern = Sinatra::Base.send(:compile, pattern).first.inspect
-        pattern.gsub! /^\/(\^|\\A)?|(\$|\\z)?\/$/, ''
-        Regexp.new pattern
+        Mustermann.new(a.to_s + b.to_s, type: :regular)
       end
 
       def prefixed(method, pattern = nil, conditions = {}, &block)

sinatra-contrib/spec/namespace_spec.rb

@@ -1,8 +1,7 @@
 require 'spec_helper'
 
 describe Sinatra::Namespace do
-  verbs = [:get, :head, :post, :put, :delete, :options]
-  verbs << :patch if Sinatra::VERSION >= '1.3'
+  verbs = [:get, :head, :post, :put, :delete, :options, :patch]
 
   def mock_app(&block)
     super do
@@ -689,7 +688,7 @@ describe Sinatra::Namespace do
             end
             get('/bar') { }
           end
-          route[1].should eq '/foo'
+          route[1].should eq Mustermann.new '/foo', type: :regular
         end
 
         specify 'prevent app-global settings from being changed' do