Clearing an iterator range

[Daniel James]

The attached test fails to compile with this error:

../quickbook-1.5/boost/spirit/home/support/attributes.hpp:710: error: 'class boost::iterator_range<const char*>' has no member named 'clear'

The problem is that iterator_range looks enough like a container so that is_container returns true, but it doesn't have a clear method. The attached patch attempts to fix this by adding a special case to clear iterator ranges.

I used a slightly odd method to clear the range, because for some reason begin is called for the cleared range (this may be a bug) and that's not allowed for default constructed ranges (since default constructed iterators can be singular).

[Hartmut Kaiser]

(In [59929]) Spirit: fixed #3815 (Clearing an iterator range)

[Hartmut Kaiser]

(In [59930]) Spirit: fixed #3815 (Clearing an iterator range), added test