PR16716 partial fix: Better types in 'syscall.{recvmsg,recvmmsg}'

PR16716 partial fix: Better types in 'syscall.{recvmsg,recvmmsg}'

* tapset/linux/syscalls2.stp: Fix types and nesting in
  'syscall.{recvmsg,compat_sys_recvmsg,recvmmsg,compat_recvmmsg}'.
* tapset/linux/nd_syscalls2.stp: Ditto.
* testsuite/systemtap.syscall/recvmmsg.c: New test.
* testsuite/systemtap.syscall/recvmsg.c: Ditto.
* testsuite/systemtap.syscall/connect.c: Updated.
* testsuite/systemtap.syscall/recv.c: Ditto.
* testsuite/systemtap.syscall/recvfrom.c: Ditto.