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/signalfd.h b/libc/include/sys/signalfd.h
index 1e4d464..315622c 100644
--- a/libc/include/sys/signalfd.h
+++ b/libc/include/sys/signalfd.h
@@ -36,8 +36,8 @@
 
 __BEGIN_DECLS
 
-int signalfd(int fd, const sigset_t* mask, int flags) __INTRODUCED_IN(18);
+int signalfd(int __fd, const sigset_t* __mask, int __flags) __INTRODUCED_IN(18);
 
 __END_DECLS
 
-#endif /* _SYS_SIGNALFD_H */
+#endif