Re-submit "Name function arguments in libc headers for Studio."

This reverts commit 9af9120091ceb96641d7c6c645fabad96db4bc0d (a revert
of 079bff4fa52b0c3c76057451cc9cdecf1827fce0), now the versioner bug is
fixed.

Bug: http://b/64613623 # header bug
Bug: http://b/64802958 # versioner bug
Change-Id: I1cb9d7832d4b3aecdc57a9285e2291443e59d02d
diff --git a/libc/include/sys/reboot.h b/libc/include/sys/reboot.h
index df4739e..c0c4860 100644
--- a/libc/include/sys/reboot.h
+++ b/libc/include/sys/reboot.h
@@ -42,8 +42,8 @@
 #define RB_DISABLE_CAD  LINUX_REBOOT_CMD_CAD_OFF
 #define RB_POWER_OFF    LINUX_REBOOT_CMD_POWER_OFF
 
-int reboot(int reboot_type);
+int reboot(int __cmd);
 
 __END_DECLS
 
-#endif /* _SYS_REBOOT_H_ */
+#endif