Add syscall test coverage per PR18151:

Add syscall test coverage per PR18151:

* tapset/linux/syscalls.stp: Fix syscall.{[compat_]lookup_dcookie,
  iopl,mincore} probes.
* tapset/linux/nd_syscalls.stp: Fix nd_syscall.{[compat_]lookup_dcookie,
  iopl,mincore} probes.
* tapset/linux/x86_64/syscalls.stp: Add syscall.compat_lookup_dcookie probe.
* tapset/linux/s390/syscalls.stp: Ditto.
* tapset/linux/powerpc/syscalls.stp: Ditto.
* tapset/linux/x86_64/nd_syscalls.stp: Add nd_syscall.compat_lookup_dcookie probe.
* tapset/linux/s390/nd_syscalls.stp: Ditto.
* tapset/linux/powerpc/nd_syscalls.stp: Ditto.
* tapset/linux/i386/syscalls.stp: Fix syscall.iopl probe.
* tapset/linux/i386/nd_syscalls.stp: Fix nd_syscall.iopl probe.
* testsuite/buildok/nd_syscalls-arch-detailed.stp: Add testcases.
* testsuite/buildok/nd_syscalls-detailed.stp: Ditto.
* testsuite/buildok/syscalls-arch-detailed.stp: Ditto.
* testsuite/buildok/syscalls-detailed.stp: Ditto.
* testsuite/systemtap.syscall/chroot.c: New testcase.
* testsuite/systemtap.syscall/dcookie.c: New testcase.
* testsuite/systemtap.syscall/forkwait.c: Cover getpid(), getppid() and gettid().
* testsuite/systemtap.syscall/ioperm.c: Cover iopl().
* testsuite/systemtap.syscall/mincore.c: New testcase.