Pattern Matching Changes

The new pattern matching implementation is now merged back into master. There are a lot changes under the hood to significantly speedup pattern matching. However, there is one change to the user interface as well: any_type no longer exists. There is a replacement though, but it's usage differs a little bit: anything.
This is a snipped using the old any_type syntax:

on<int, any_type>() >> [](int v1) { }, // 1
on<int, any_type*>() >> [](int v1) { } // 2

The semantic of the first line - matching exactly one element of any type - is no longer supported. The second line just needs to replace any_type* with anything to work:

// equal to 2
on<int, anything>() >> [](int v1) { }

This will match any message with an integer as first element.