[libclang] Introduce clang_Cursor_isObjCOptional, which returns whether the declaration was affected by "@optional"

rdar://14348525.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@185722 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/c-index-test/c-index-test.c b/tools/c-index-test/c-index-test.c
index a824a9f..2e8b58b 100644
--- a/tools/c-index-test/c-index-test.c
+++ b/tools/c-index-test/c-index-test.c
@@ -698,7 +698,9 @@
       printf(" (pure)");
     if (clang_Cursor_isVariadic(Cursor))
       printf(" (variadic)");
-    
+    if (clang_Cursor_isObjCOptional(Cursor))
+      printf(" (@optional)");
+
     if (Cursor.kind == CXCursor_IBOutletCollectionAttr) {
       CXType T =
         clang_getCanonicalType(clang_getIBOutletCollectionType(Cursor));