Input framework now accepts escaped ascii values as input.

I managed to completely forget to add unescaping to the input framework -
this should fix it. It now works with the exact same escaping that is
used by the writers (\x##).

Includes one testcase that seems to work - everything else still passes.

src/util.h

@@ -90,6 +90,7 @@ void delete_each(T* t)
 		delete *it;
 	}
 
+std::string get_unescaped_string(const std::string& str);
 std::string get_escaped_string(const std::string& str, bool escape_all);
 
 extern char* copy_string(const char* s);