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/1145-swift-constraints-constraintsystem-addconstraint.swift

@@ -0,0 +1,12 @@
+// 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
+
+func j<m>(g: j.e) -> m! {n : h -> h = {
+}(k, q)
+protocol h : f { func f
+v -  }
+}
+false