Currently 'perf test llvm' and 'perf test BPF' have multiple sub-tests,
but the result is provided in only one line:

  # perf test LLVM
  35: Test LLVM searching and compiling                        : Ok

This patch introduces sub-tests support, allowing 'perf test' to report
result for each sub-tests:

  # perf test LLVM
  35: Test LLVM searching and compiling                        :
  35.1: Basic BPF llvm compiling test                          : Ok
  35.2: Test kbuild searching                                  : Ok
  35.3: Compile source for BPF prologue generation test        : Ok

When a failure happens:

  # cat ~/.perfconfig
  [llvm]
       clang-path = "/bin/false"
  # perf test LLVM
  35: Test LLVM searching and compiling                        :
  35.1: Basic BPF llvm compiling test                          : FAILED!
  35.2: Test kbuild searching                                  : Skip
  35.3: Compile source for BPF prologue generation test        : Skip

And:

  # rm ~/.perfconfig
  # ./perf test LLVM
  35: Test LLVM searching and compiling                        :
  35.1: Basic BPF llvm compiling test                          : Skip
  35.2: Test kbuild searching                                  : Skip
  35.3: Compile source for BPF prologue generation test        : Skip

Skip by user:

  # ./perf test -s 1,`seq -s , 3 42`
   1: vmlinux symtab matches kallsyms                          : Skip (user override)
   2: detect openat syscall event                              : Ok
  ...
  35: Test LLVM searching and compiling                        : Skip (user override)
  ...
Suggested-and-Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1447749170-175898-4-git-send-email-wangnan0@huawei.com
[ Changed so that func is not on an anonymous union ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>