attributes string ascii escape "&#nn;" shouldn't throw exception

[kondo@…]

In boost/property_tree/detail/rapidxml.hpp

At member function template

template<class StopPred, class StopPredPure, int Flags>
static Ch *skip_and_expand_character_refs(Ch *&text)

It supports escape "&", """, ">", "<" and "&#nn;". (nn is number, xnn is also supported. When the member function template find the charactor '&' it starts parsing. And if it couldn't find the correct match, escape string is ignore and just copy '&' verbatim. But in the case of "&#nn", the error below would occur. And this error throw the parse_error exception.

BOOST_PROPERTY_TREE_RAPIDXML_PARSE_ERROR("expected ;", src);

I expect just ignore instead of the error. This behavior is same as other escape string's manner.

I attached patch. Could you check it?