Refs. #8614. Width specification now works correctly for strings.

svn path=/trunk/boost/log/; revision=84512
write() no longer asserts when the stream wrapper is not attached to a string. Rather, it behaves more like a standard stream write() when the stream is bad.

svn path=/trunk/boost/log/; revision=84514
Fall back to portable implementation of unhandled_exception_count() on MinGW GCC 4.4 as it seems to not work the same way as the newer versions of GCC do.

svn path=/trunk/libs/log/; revision=84515