Wrap tune2fs.h to be C++ compatible.

Change-Id: I5d1bf4913ebe8f072ac8d31149ba97e876c8a595
(cherry picked from commit b0af72276f654c4d5f9bd0756802115a83437b82)
diff --git a/misc/tune2fs.h b/misc/tune2fs.h
index 897e336..7b7e431 100644
--- a/misc/tune2fs.h
+++ b/misc/tune2fs.h
@@ -7,7 +7,20 @@
  * %End-Header%
  */
 
+#ifndef _TUNE2FS_H_
+#define _TUNE2FS_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* Takes exactly the same args as the tune2fs exectuable.
  * Is the entrypoint for libtune2fs.
  */
 int tune2fs_main(int argc, char **argv);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif