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/mount.h b/libc/include/sys/mount.h
index 26c0e0f..c0c084b 100644
--- a/libc/include/sys/mount.h
+++ b/libc/include/sys/mount.h
@@ -41,10 +41,10 @@
 #define MNT_EXPIRE 4
 #define UMOUNT_NOFOLLOW 8
 
-int mount(const char*, const char*, const char*, unsigned long, const void*);
-int umount(const char*);
-int umount2(const char*, int);
+int mount(const char* __source, const char* __target, const char* __fs_type, unsigned long __flags, const void* __data);
+int umount(const char* __target);
+int umount2(const char* __target, int __flags);
 
 __END_DECLS
 
-#endif /* _SYS_MOUNT_H */
+#endif