stdlib/printing: remove ReplPrintable protocol
stdlib/printing: remove ReplPrintable protocol

It is replaced by debugPrint() family of functions, that are called by REPL.

There is a regression in printing types that don't conform to Printable, this
is tracked by rdar://16898708


Swift SVN r18006

apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation