Remove @transparent from a few functions in the stdlib.

Marking these generic functions as transparent results in our not
emitting diagnostics for unreachable code if these functions are the
only code in a block and inlining generic code is enabled (due to
<rdar://problem/17687851>).

I don't believe other diagnostics benefit in any way from having these
marked as @transparent, and removing @transparent actually improved
Ackerman at -O3 by 15%.

Swift SVN r19996

stdlib/core/Index.swift

@@ -100,13 +100,13 @@ public protocol _ForwardIndexType : _Incrementable {
   typealias _DisabledRangeIndex = _DisabledRangeIndex_
 }
 
-@transparent prefix public
+prefix public
 func ++ <T : _Incrementable> (inout x: T) -> T {
   x = x.successor()
   return x
 }
 
-@transparent postfix public
+postfix public
 func ++ <T : _Incrementable> (inout x: T) -> T {
   var ret = x
   x = x.successor()
@@ -192,14 +192,14 @@ public protocol _BidirectionalIndexType : _ForwardIndexType {
 public protocol BidirectionalIndexType 
   : ForwardIndexType, _BidirectionalIndexType {}
 
-@transparent public
+public
 prefix func -- <T: _BidirectionalIndexType> (inout x: T) -> T {
   x = x.predecessor()
   return x
 }
 
 
-@transparent public
+public
 postfix func -- <T: _BidirectionalIndexType> (inout x: T) -> T {
   var ret = x
   x = x.predecessor()
@@ -284,4 +284,3 @@ func ~> <T: _RandomAccessIndexType>(
   let d = start.distanceTo(end)
   return (n > 0 ? d < n : d > n) ? end : start.advancedBy(n)
 }
-