perf top: Show backtrace when handling a SIGSEGV on --stdio mode
perf top: Show backtrace when handling a SIGSEGV on --stdio mode

It was just freezing instead of informing about the SEGV, fix it and
also print a backtrace, just like in the TUI mode and in 'perf trace'.

Tested by provoking a NULL deref when pressing 'z':

     0.31%  libc-2.20.so     [.] malloc_consolidate
     0.31%  ld-2.20.so       [.] _dl_relocate_object
     0.28%  cc1              [.] ht_lookup
     0.28%  cc1              [.] ira_init_register_move_cost
  perf: Segmentation fault
  Obtained 7 stack frames.
  perf(dump_stack+0x32) [0x4d69f2]
  perf(sighandler_dump_stack+0x29) [0x4d6a89]
  /lib64/libc.so.6(+0x34960) [0x7f5064333960]
  perf() [0x438790]
  /lib64/libpthread.so.0(+0x752a) [0x7f50663dd52a]
  /lib64/libc.so.6(clone+0x6d) [0x7f50643ff22d]
  #

Reported-by: Linus Torvalds <69652caca27c8b940640ad396ab71f93cacec34f@linux-foundation.org>
Cc: Adrian Hunter <41bb5944f244750b7cf0394140496972a3f1bee3@intel.com>
Cc: Borislav Petkov <0691a664b24b6f15b20cd5aee64b72271db08be1@suse.de>
Cc: David Ahern <b80c1600f604d3b0d768f26f90a76757e76005dd@gmail.com>
Cc: Frederic Weisbecker <e8a1bf9163cb25e93cfd6540f223b3872ea7ee55@gmail.com>
Cc: Jiri Olsa <2c6594f608aa3d41e98d48846a6328831f7084ad@redhat.com>
Cc: Namhyung Kim <5c915a589b3ddf58cebf14bec41bcc143b37ac3c@kernel.org>
Cc: Stephane Eranian <f199ae9781930a5b94b284ca2f471140752002a7@google.com>
Link: f2e0c480cb193d3faf15a79ee977f28374f7627d@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <293abb6b76d7791c0732cc517d38c4b5c734b87f@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs