Add basic compilation tests from swift-compiler-crashes (https://github.com/practicalswift/swift-compiler-crashes.git)

Swift SVN r21693

validation-test/compiler_crashers/030-string-as-extensibe-collection.script.swift

@@ -0,0 +1,8 @@
+// RUN: %swift %s -emit-ir
+// Test case submitted to project by https://github.com/tmu (Teemu Kurppa)
+
+func f<S : ExtensibleCollectionType>(seq: S) -> S {
+    return S() + seq
+}
+
+f("a")