add sample script scripts/syscalls/opensnoop.kp

This script is contributed by Brendan Gregg.
	http://www.brendangregg.com/ktap/opensnoop.kp

opensnoop.kp: trace open() syscalls and print basic details.
Useful for debugging as it can quickly show which data files,
log files, and config files are in use by an application.

Example:
[root@localhost ktap]# ./ktap -q scripts/syscalls/opensnoop.kp
    UID    PID COMM          FD ERR PATH
      0  11491 ktap           5   0 /sys/kernel/debug/ktap/trace_pipe_11490
      0    994 sendmail       6   0 /proc/loadavg
      0    598 irqbalance     3   0 /proc/interrupts
      0    598 irqbalance     3   0 /proc/stat
      0    598 irqbalance     3   0 /proc/irq/9/smp_affinity
      0    598 irqbalance     3   0 /proc/irq/72/smp_affinity
      0    598 irqbalance     3   0 /proc/irq/73/smp_affinity
      0    598 irqbalance     3   0 /proc/irq/17/smp_affinity
      0    598 irqbalance     3   0 /proc/irq/40/smp_affinity

[root@localhost ktap]# ./ktap -q scripts/syscalls/opensnoop.kp -- ls > /dev/null
    UID    PID COMM          FD ERR PATH
      0  11502 ls             5   0 /etc/ld.so.cache
      0  11502 ls             5   0 /lib64/libselinux.so.1
      0  11502 ls             5   0 /lib64/librt.so.1
      0  11502 ls             5   0 /lib64/libcap.so.2
      0  11502 ls             5   0 /lib64/libacl.so.1
      0  11502 ls             5   0 /lib64/libc.so.6
      0  11502 ls             5   0 /lib64/libpcre.so.1
      0  11502 ls             5   0 /lib64/libdl.so.2
      0  11502 ls             5   0 /lib64/libpthread.so.0
      0  11502 ls             5   0 /lib64/libattr.so.1
      0  11502 ls             5   0

Signed-off-by: Jovi Zhangwei <jovi.zhangwei@gmail.com>