immutability of the pointed-to type via const qualification. The
pointee of a proxy-based iterator will be const qualified unless a
mutable reference to the value_type can be bound to the returned
proxy.
Added a test for pointee
Fixed iterator_facade so operator[] result type computation didn't
cause a problem with abstract types.
Updated iterator_facade operator[] docs for accuracy.
Allowed Borland to simply fail the indirect_iterator_member_types test
because of its lame const-dropping, instead of trying to work around
it.
[SVN r21579]