perf_event__process_feature() accesses feat_ops[HEADER_LAST_FEATURE]
which is not defined and thus perf is crashing. HEADER_LAST_FEATURE is
used as an end marker for the perf report but it's unused for perf
script/annotate. Ignore HEADER_LAST_FEATURE for perf script/annotate,
just like it is done in 'perf report'.

Before:
  # perf record -o - ls | perf script
  <SNIP 'ls' output>
  Segmentation fault (core dumped)
  #

After:
  # perf record -o - ls | perf script
  <SNIP 'ls' output>
  Segmentation fault (core dumped)
  ls 7031 4392.099856:  250000 cpu-clock:uhH:  7f5e0ce7cd60
  ls 7031 4392.100355:  250000 cpu-clock:uhH:  7f5e0c706ef7
  #
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: David Carrillo-Cisneros <davidcc@google.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Fixes: 57b5de46 ("perf report: Support forced leader feature in pipe mode")
Link: http://lkml.kernel.org/r/20180625124220.6434-4-ravi.bangoria@linux.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>