[boost] [Exception] SFINAE use breaks Borland in Trunk

Boost.Exception is currently failing for Borland compiles with for example: http://tinyurl.com/ycu779q The issue appears to be use of SFINAE like techniques without a BOOST_NO_SFINAE fallback. The problem here is that since Boost.Exception gets pulled in by almost everything, we need it to be lightweight and well supported, otherwise the rest of us are stuck even if we want to continue to support the older compilers :-( Thanks! John.