PR18184: Test coverage improvements, tapset extension.

PR18184: Test coverage improvements, tapset extension.

* tapset/linux/aux_syscalls.stp: Add auxiliary functions for quotactl tapset.
* tapset/linux/nd_syscalls2.stp: Fix types for personality tapset,
                                 extend argstr for quotactl.
* tapset/linux/syscalls2.stp: Ditto.
* tapset/linux/syscalls.stpm: New macro @__quotactl_argstr().
* testsuite/systemtap.syscall/personality.c: New testcase.
* testsuite/systemtap.syscall/pivot_root.c: New testcase.
* testsuite/systemtap.syscall/quotactl.c: Testcase extension.