libsparse: deal with build warning messages

- mostly unused parameters, added defs.h to hold __unused macro
- read_all prototype not included, added output_file.h to acquire

Change-Id: Ib7ee00614acab53a6bd6a64f7e26a8c13dbe6297
diff --git a/libsparse/defs.h b/libsparse/defs.h
new file mode 100644
index 0000000..34e63c5
--- /dev/null
+++ b/libsparse/defs.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _LIBSPARSE_DEFS_H_
+
+#ifndef __unused
+#define __unused        __attribute__((__unused__))
+#endif
+
+#endif /* _LIBSPARSE_DEFS_H_ */