Add test that we still import Clang decls with rejected SwiftName API…

… notes.

Most cases fall out from swift_name validation on the Clang side dropping invalid API notes, though the validation on the Clang side is conservative and misses some cases. We still have Swift-side work to fall back to the original name here.

test/APINotes/broken-swift-name.swift

@@ -13,4 +13,12 @@ func testBrokenSwiftName(x: inout ZXSpectrum) {
 
   _ = x.misnamedRegister // expected-error{{has no member}}
   x.misnamedRegister = 0 // expected-error{{has no member}}
+
+  // Ensure that definitions with invalid API notes are still available
+  // under their original names.
+  ZXSpectrumGetRegister(&x, 0)
+  ZXSpectrumSetRegister(&x, 0, 1)
+  ZXSpectrumGetMisnamedRegister(&x, 0)
+  // TODO: Conservative validation in Clang doesn't reject the API name here
+  // ZXSpectrumSetMisnamedRegister(&x, 0, 1)
 }