perf tests: Adding automated parsing tests for group :GH modifiers

perf tests: Adding automated parsing tests for group :GH modifiers

The ':GH' group modifier handling was just recently fixed, adding some
autommated tests to keep it that way. Adding tests for following events:

  "{cycles,cache-misses:G}:H"
  "{cycles,cache-misses:H}:G"
  "{cycles:G,cache-misses:H}:u"
  "{cycles:G,cache-misses:H}:uG"

Plus fixing test__group2 test.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1359971803-2343-3-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>