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/0148-swift-parser-parseexprunary.swift

@@ -0,0 +1,21 @@
+// 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
+
+}
+e
+protocol h : e { func e
+func r(d: t, k: t) -> (((t, t) -> t) -i g {
+    p m
+    func e(m)
+}
+struct e<j> : g {
+    func e(
+h s: n -> n = {
+    return $u
+}
+l o: n = { (d: n, o: n -> n) -> n q
+    return o(d)
+}