Import the swift-compiler-crashes test suite.

Add all compiler crash tests to the validation-test/compiler_crashers
subdirectory. Add a RUN: line to each test case according to the current
behavior of the Swift compiler.

Swift SVN r23418

validation-test/compiler_crashers/1324-swift-constraints-constraintgraph-removeconstraint.swift

@@ -0,0 +1,24 @@
+// RUN: not --crash %swift %s -parse
+
+// Distributed under the terms of the MIT license
+// Test case submitted to project by https://github.com/practicalswift (practicalswift)
+// Test case found by fuzzing
+
+typealias C {
+self.<j : () {
+}
+}
+protocol a {
+typealias f : $0) -> T -> {
+0) -> {
+let t: start, e> (T>()) {
+}
+}
+}
+typealias d: b.startIndex)""")
+extension NSSet {
+func f: B(h: c<3] = {
+}
+func a))
+}
+class func b<T,