Add support to add/remove fields for specific event types in -F option.
It's now possible to use '+-' after event type, like:

  # cat > test.c
  #include <stdio.h>

  int main(void)
  {
     printf("Hello world\n");
     while(1) {}
  }
  ^D
  # gcc -g -o test test.c
  # perf probe -x test 'test.c:5'
  # perf record -e '{cpu/cpu-cycles,period=10000/,probe_test:main}:S' ./test
  ...

  # perf script -Ftrace:+period,-cpu
            test  3859 396291.117343:      10275 cpu/cpu-cycles,period=10000/:      7f..
            test  3859 396291.118234:      11041 cpu/cpu-cycles,period=10000/:  ffffff..
            test  3859 396291.118234:          1              probe_test:main:
            test  3859 396291.118248:       8668 cpu/cpu-cycles,period=10000/:  ffffff..
            test  3859 396291.118263:      10139 cpu/cpu-cycles,period=10000/:  ffffff..

Committer testing:

Couldn't make the test above work, but tested it with:

  # perf probe -x hello main
  Added new event:
    probe_hello:main     (on main in /home/acme/c/hello)

  You can now use it in all perf tools, such as:

	  perf record -e probe_hello:main -aR sleep 1

  # perf record -e probe_hello:main ./hello
  hello, world
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.025 MB perf.data (1 samples) ]
  # perf script
           hello 21454 [002] 254116.874005: probe_hello:main: (401126)
  #
  # perf script -Ftrace:+period,-cpu
           hello 21454 254116.874005:          1 probe_hello:main: (401126)
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190220122800.864-4-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>