Merge pull request #5646 from practicalswift/swiftc-28469-segfault-0x4674de-0x464be6

[swiftc (99 vs. 5181)] Add crasher in swift::TypeBase::getCanonicalType(...)

Author: practicalswift

validation-test/compiler_crashers/28469-segfault-0x4674de-0x464be6.swift

@@ -0,0 +1,9 @@
+// This source file is part of the Swift.org open source project
+// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+// RUN: not --crash %target-swift-frontend %s -emit-ir
+protocol C{func^extension{func^