e47a604197
sys_timerfd was fully implemented in Rust (timerfd_create, timerfd_settime, timerfd_gettime, itimerspec support) but lacked the cbindgen.toml needed to generate the <sys/timerfd.h> C header. Qt6's QSocketNotifier and many other C programs depend on this header. Without it, cbindgen skips the directory entirely. This adds the cbindgen config + trailer with all function prototypes, matching the pattern used by sys_signalfd.