Add rotl function

Added Rotate left function which takes a value (a) to rotate and an amount (b) to rotate the value (a). The function returns the rotated (a).

Sources/CryptoSwift/Foundation/Utils+Foundation.swift

@@ -25,3 +25,7 @@ func perf(_ text: String, closure: () -> Void) {
 
     print("\(text) \(executionTime)")
 }
+
+func rotl(_ a: UInt32, _ b: Int) -> UInt32 {
+    return (a << b) | (a >> (32 - b))
+}