Introduce a new 'renamed' modifier on unavailable attributes. This allows Xcode

to emit fixit's when we rename something, e.g.:

t.swift:6:9: error: 'float' has been renamed to Float
var y : float
        ^~~~~
        Float

Adopt this in the stdlib.



Swift SVN r20549

include/swift/Serialization/ModuleFormat.h

@@ -1071,6 +1071,7 @@ namespace decls_block {
     BC_AVAIL_TUPLE, // Obsoleted
     BCVBR<5>,   // platform
     BCVBR<5>,   // number of bytes in message string
+    BCVBR<5>,   // number of bytes in rename string
     BCBlob      // platform, followed by message
   >;