swift234

[swiftc] Add test case for crash triggered in swift::IterativeTypeChecker::satisfy(swift::TypeCheckRequest)

Stack trace:

```
swift: /path/to/swift/lib/Sema/IterativeTypeChecker.cpp:103: void swift::IterativeTypeChecker::satisfy(swift::TypeCheckRequest): Assertion `isSatisfied(request)' failed.
9  swift           0x0000000000f3f3b9 swift::IterativeTypeChecker::satisfy(swift::TypeCheckRequest) + 889
10 swift           0x0000000000f3f3b9 swift::IterativeTypeChecker::satisfy(swift::TypeCheckRequest) + 889
13 swift           0x0000000000e3f115 swift::TypeChecker::validateDecl(swift::ValueDecl*, bool) + 3749
16 swift           0x0000000000e43ed6 swift::TypeChecker::typeCheckDecl(swift::Decl*, bool) + 150
17 swift           0x0000000000e67142 swift::performTypeChecking(swift::SourceFile&, swift::TopLevelContext&, swift::OptionSet<swift::TypeCheckingFlags, unsigned int>, unsigned int) + 1026
18 swift           0x0000000000cb9d8f swift::CompilerInstance::performSema() + 3087
20 swift           0x000000000078ab9b frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 2523
21 swift           0x0000000000785645 main + 2837
Stack dump:
0.	Program arguments: /path/to/swift/bin/swift -frontend -c -primary-file validation-test/compiler_crashers/28261-swift-iterativetypechecker-satisfy.swift -target x86_64-unknown-linux-gnu -disable-objc-interop -module-name main -o /tmp/28261-swift-iterativetypechecker-satisfy-2b2db1.o
1.	While type-checking 'F' at validation-test/compiler_crashers/28261-swift-iterativetypechecker-satisfy.swift:8:1
2.	While type-checking 'F' at validation-test/compiler_crashers/28261-swift-iterativetypechecker-satisfy.swift:8:1
<unknown>:0: error: unable to execute command: Aborted
<unknown>:0: error: compile command failed due to signal (use -v to see invocation)
```