Teach Diagnostic::setClient() to free the existing, owned
client. Fixes a libclang leak.

llvm-svn: 124614
diff --git a/clang/tools/c-index-test/c-index-test.c b/clang/tools/c-index-test/c-index-test.c
index 808f4e9..8c87d37 100644
--- a/clang/tools/c-index-test/c-index-test.c
+++ b/clang/tools/c-index-test/c-index-test.c
@@ -827,6 +827,8 @@
   }
 
   fclose(fp);
+  clang_disposeTranslationUnit(TU);
+  clang_disposeIndex(Idx);
   return 0;
 }