Add regression test for fixed crasher

This was fixed by 89f5066fb4.

validation-test/compiler_crashers_2_fixed/rdar146681539.swift

@@ -0,0 +1,22 @@
+// RUN: %target-typecheck-verify-swift
+
+protocol Q {
+  func foo()
+}
+
+protocol P<T>: AnyObject {
+  associatedtype T: Q
+}
+
+final class C<T: Q>: P {
+}
+
+struct S: Q {
+  func foo() {}
+}
+
+// This used to return an ErrorType and crash
+
+func testit() -> P<S> {  // expected-warning {{use of protocol 'P' as a type must be written 'any P'}}
+  return C<S>()
+}