remove legacy time32 timer[fd] syscalls from public syscall.h

remove legacy time32 timer[fd] syscalls from public syscall.h

this extends commit 5a105f19b5aae79dd302899e634b6b18b3dcd0d6, removing
timer[fd]_settime and timer[fd]_gettime. the timerfd ones are likely
to have been used in software that started using them before it could
rely on libc exposing functions.