Name function arguments in libc headers for Studio.

Second batch of headers...

Bug: http://b/64613623
Test: builds
Change-Id: I8eef043dbf32afee8ff814e9d005f46aee8fa21f
diff --git a/libc/include/sys/prctl.h b/libc/include/sys/prctl.h
index 742ed57..64f5954 100644
--- a/libc/include/sys/prctl.h
+++ b/libc/include/sys/prctl.h
@@ -35,8 +35,8 @@
 
 __BEGIN_DECLS
 
-int prctl(int option, ...);
+int prctl(int __option, ...);
 
 __END_DECLS
 
-#endif /* _SYS_PRCTL_H */
+#endif