Merge pull request #3042 from practicalswift/swiftc-28316-swift-typechecker-checkgenericparamlist

[swiftc] Add 💥 case (😢 → 93, 😀 → 5067) triggered in swift::TypeCheck::checkGenericParamList(…)

Author: slavapestov

validation-test/compiler_crashers/28316-swift-typechecker-checkgenericparamlist.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 -parse
+{class B{init(T)}class T where g:a