Ruiby-quota dosen't compile on newer operating systems. Here is a patch to fix these problem.
* Compile problem on NetBSD 4.0 and later.
* Compile problem on DragonFly BSD.
* Compile problem on Linux 2.6.x.
* Module's version is still "0.4.1" although this extention module's version os "0.5.1".
* Portability fix in rb_quotactl().
Attached patch would be fix these problems.