Add validation test under compiler crashers fixed

Author: zoecarver

validation-test/compiler_crashers_2_fixed/sr11624.swift

@@ -0,0 +1,20 @@
+// This source file is part of the Swift.org open source project
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+// RUN: not %target-swift-frontend %s -O -whole-module-optimization
+
+class ClassA<T> { }
+protocol ProtocolA { }
+
+class MainClass<H> {
+    init(x: ClassA<H> & ProtocolA) { }
+}
+
+final class ClassB: ClassA<String> { }
+extension ClassB: ProtocolA { }
+
+_ = MainClass(x: ClassB())