libc: remove C++ comments from public headers.

Change-Id: I4af84f912062cd2ff34711c25122fb323f20c032
diff --git a/libc/include/sys/ptrace.h b/libc/include/sys/ptrace.h
index 78a057a..848416b 100644
--- a/libc/include/sys/ptrace.h
+++ b/libc/include/sys/ptrace.h
@@ -30,7 +30,7 @@
 
 #include <sys/cdefs.h>
 #include <sys/types.h>
-// For all of the defines
+/* For all of the defines */
 #include <linux/ptrace.h>
 
 __BEGIN_DECLS