arm, sparc, sparc64: wire up io_pgetevents

arm, sparc, sparc64: wire up io_pgetevents

* linux/arm/syscallent.h ([399]): Wire up io_pgetevents syscall
introduced by Linux commit v4.19-rc7~24^2~1.
(ARM_FIRST_SHUFFLED_SYSCALL, SYS_socket_subcall): Raise from 400 to 500,
to make room for new syscalls.
* linux/sparc/syscallent.h ([361]): Wire up io_pgetevents syscall
introduced by Linux commit v4.19~31^2~5.
* linux/sparc64/syscallent.h: Likewise.