Tag everything in the standard library with accessibility attributes.

Keep calm: remember that the standard library has many more public exports
than the average target, and that this contains ALL of them at once.
I also deliberately tried to tag nearly every top-level decl, even if that
was just to explicitly mark things @internal, to make sure I didn't miss
something.

This does export more than we might want to, mostly for protocol conformance
reasons, along with our simple-but-limiting typealias rule. I tried to also
mark things private where possible, but it's really going to be up to the
standard library owners to get this right. This is also only validated
against top-level access control; I haven't fully tested against member-level
access control yet, and none of our semantic restrictions are in place.

Along the way I also noticed bits of stdlib cruft; to keep this patch
understandable, I didn't change any of them.

Swift SVN r19145

stdlib/core/CString.swift

@@ -25,18 +25,18 @@
 /// * it may not contain well-formed UTF-8.  Because of this, comparison
 ///   operators `<` and `==` on `CString` use `strcmp` instead of Unicode
 ///   comparison algorithms.
-struct CString :
+@public struct CString :
     _BuiltinExtendedGraphemeClusterLiteralConvertible,
     ExtendedGraphemeClusterLiteralConvertible,
     _BuiltinStringLiteralConvertible, StringLiteralConvertible,
     LogicValue {
   var _bytesPtr: UnsafePointer<UInt8>
 
-  init(_ bytesPtr: UnsafePointer<UInt8>) {
+  @public init(_ bytesPtr: UnsafePointer<UInt8>) {
     self._bytesPtr = bytesPtr
   }
 
-  init(_ bytesPtr: UnsafePointer<CChar>) {
+  @public init(_ bytesPtr: UnsafePointer<CChar>) {
     self._bytesPtr = UnsafePointer<UInt8>(bytesPtr)
   }
 
@@ -49,7 +49,7 @@ struct CString :
                                             isASCII: isASCII)
   }
 
-  static func convertFromExtendedGraphemeClusterLiteral(
+  @public static func convertFromExtendedGraphemeClusterLiteral(
     value: CString) -> CString {
 
     return convertFromStringLiteral(value)
@@ -61,7 +61,7 @@ struct CString :
     return CString(UnsafePointer<CChar>(start))
   }
 
-  static func convertFromStringLiteral(value: CString) -> CString {
+  @public static func convertFromStringLiteral(value: CString) -> CString {
     return value
   }
 
@@ -70,7 +70,7 @@ struct CString :
     return _bytesPtr._isNull
   }
 
-  @transparent
+  @transparent @public
   func getLogicValue() -> Bool {
     return !_isNull
   }
@@ -78,7 +78,7 @@ struct CString :
   /// From a non-`nil` `CString` with possibly-transient lifetime, create a
   /// nul-terminated array of 'C' char.
   /// Returns `nil` if the `CString` was created from a null pointer.
-  func persist() -> CChar[]? {
+  @public func persist() -> CChar[]? {
     if !self {
       return .None
     }
@@ -93,7 +93,7 @@ struct CString :
 }
 
 extension CString : DebugPrintable {
-  var debugDescription: String {
+  @public var debugDescription: String {
     let (optionalString, hadError) =
         String.fromCStringRepairingIllFormedUTF8(self)
     if let s = optionalString {
@@ -110,19 +110,19 @@ func _strcpy(dest: CString, src: CString) -> CString
 @asmname("strcmp")
 func _strcmp(dest: CString, src: CString) -> CInt
 
-@transparent
+@transparent @public
 func ==(lhs: CString, rhs: CString) -> Bool {
   if lhs._bytesPtr == rhs._bytesPtr { return true }
   return _strcmp(lhs, rhs) == 0
 }
 
-@transparent
+@transparent @public
 func <(lhs: CString, rhs: CString) -> Bool {
   return _strcmp(lhs, rhs) < 0
 }
 
 extension CString : Equatable, Hashable, Comparable {
-  @transparent
+  @transparent @public
   var hashValue: Int {
     if let s = String.fromCStringRepairingIllFormedUTF8(self).0 {
       return s.hashValue
@@ -137,7 +137,7 @@ extension String {
   ///
   /// Returns `nil` if the `CString` is `NULL` or if it contains ill-formed
   /// UTF-8 code unit sequences.
-  static func fromCString(cs: CString) -> String? {
+  @public static func fromCString(cs: CString) -> String? {
     if cs._isNull {
       return .None
     }
@@ -152,7 +152,7 @@ extension String {
   /// Returns `nil` if the `CString` is `NULL`.  If `CString` contains
   /// ill-formed UTF-8 code unit sequences, replaces them with replacement
   /// characters (U+FFFD).
-  static func fromCStringRepairingIllFormedUTF8(cs: CString)
+  @public static func fromCStringRepairingIllFormedUTF8(cs: CString)
       -> (String?, hadError: Bool) {
     if cs._isNull {
       return (.None, hadError: false)