[swiftc] Add test case for crash triggered in swift::TypeChecker::checkGenericParamList(swift::ArchetypeBuilder*, swift::GenericParamList*, swift::GenericSignature*, bool, swift::GenericTypeResolver*)

Stack trace:

```
4  swift           0x0000000000ed89bd swift::TypeChecker::checkGenericParamList(swift::ArchetypeBuilder*, swift::GenericParamList*, swift::GenericSignature*, bool, swift::GenericTypeResolver*) + 93
6  swift           0x0000000000ed90de swift::TypeChecker::validateGenericFuncSignature(swift::AbstractFunctionDecl*) + 94
9  swift           0x0000000000e9b741 swift::TypeChecker::validateDecl(swift::ValueDecl*, bool) + 1089
10 swift           0x00000000010f587c swift::DeclContext::lookupQualified(swift::Type, swift::DeclName, swift::NLOptions, swift::LazyResolver*, llvm::SmallVectorImpl<swift::ValueDecl*>&) const + 2652
11 swift           0x0000000000edcf37 swift::TypeChecker::lookupMemberType(swift::DeclContext*, swift::Type, swift::Identifier, swift::OptionSet<swift::NameLookupFlags, unsigned int>) + 295
13 swift           0x0000000000f0d47e swift::TypeChecker::resolveIdentifierType(swift::DeclContext*, swift::IdentTypeRepr*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, bool, swift::GenericTypeResolver*, llvm::function_ref<bool (swift::TypeCheckRequest)>*) + 158
15 swift           0x0000000000f0e554 swift::TypeChecker::resolveType(swift::TypeRepr*, swift::DeclContext*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, swift::GenericTypeResolver*, llvm::function_ref<bool (swift::TypeCheckRequest)>*) + 164
16 swift           0x0000000000f0d370 swift::TypeChecker::validateType(swift::TypeLoc&, swift::DeclContext*, swift::OptionSet<swift::TypeResolutionFlags, unsigned int>, swift::GenericTypeResolver*, llvm::function_ref<bool (swift::TypeCheckRequest)>*) + 192
17 swift           0x0000000000e9953a swift::TypeChecker::checkInheritanceClause(swift::Decl*, swift::GenericTypeResolver*) + 5370
18 swift           0x0000000000e9b50f swift::TypeChecker::validateDecl(swift::ValueDecl*, bool) + 527
21 swift           0x0000000000ea0c86 swift::TypeChecker::typeCheckDecl(swift::Decl*, bool) + 150
24 swift           0x0000000000f060aa swift::TypeChecker::typeCheckFunctionBodyUntil(swift::FuncDecl*, swift::SourceLoc) + 346
25 swift           0x0000000000f05f0e swift::TypeChecker::typeCheckAbstractFunctionBodyUntil(swift::AbstractFunctionDecl*, swift::SourceLoc) + 46
26 swift           0x0000000000f06ad3 swift::TypeChecker::typeCheckAbstractFunctionBody(swift::AbstractFunctionDecl*) + 179
28 swift           0x0000000000ec3761 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int, unsigned int) + 1281
29 swift           0x0000000000c58169 swift::CompilerInstance::performSema() + 3289
31 swift           0x00000000007d7499 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2857
32 swift           0x00000000007a34b8 main + 2872
Stack dump:
0.	Program arguments: /path/to/swift/bin/swift -frontend -c -primary-file validation-test/compiler_crashers/28312-swift-typechecker-checkgenericparamlist.swift -target x86_64-unknown-linux-gnu -disable-objc-interop -module-name main -o /tmp/28312-swift-typechecker-checkgenericparamlist-dcf2e2.o
1.	While type-checking getter for w at validation-test/compiler_crashers/28312-swift-typechecker-checkgenericparamlist.swift:10:6
2.	While type-checking 'c' at validation-test/compiler_crashers/28312-swift-typechecker-checkgenericparamlist.swift:10:7
3.	While resolving type A.b at [validation-test/compiler_crashers/28312-swift-typechecker-checkgenericparamlist.swift:10:15 - line:10:17] RangeText="A.b"
4.	While type-checking 'b' at validation-test/compiler_crashers/28312-swift-typechecker-checkgenericparamlist.swift:10:27
<unknown>:0: error: unable to execute command: Segmentation fault
<unknown>:0: error: compile command failed due to signal (use -v to see invocation)
```

Author: practicalswift

validation-test/compiler_crashers/28312-swift-typechecker-checkgenericparamlist.swift

@@ -0,0 +1,10 @@
+// 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
+// REQUIRES: asserts
+let w{class c:A.b:class A{func b where h=c