[stdlib] Add policies for Callable things as a workaround for <rdar://problem/13251236>

(remapping bound function type not implemented yet)

Swift SVN r5454

test/stdlib/Algorithm.swift

@@ -0,0 +1,18 @@
+// RUN: %swift -i %s | FileCheck %s
+
+struct IsSpace : Predicate {
+  typealias Arguments = CodePoint
+  typealias Result = Bool
+  func __call__(c: CodePoint) -> Result {
+    return c.isSpace()
+  }
+}
+
+func testApply() {
+  // CHECK: false
+  println(apply(IsSpace(), 'x'))
+
+  // CHECK: true
+  println(apply(IsSpace(), '\n'))
+}
+testApply()