perf util: Create branch.c/.h for common branch functions

perf util: Create branch.c/.h for common branch functions

Create new util/branch.c and util/branch.h to contain the common branch
functions. Such as:

branch_type_count(): Count the numbers of branch types
branch_type_name() : Return the name of branch type
branch_type_stat_display(): Display branch type statistics info
branch_type_str(): Construct the branch type string.

The branch type is saved in branch_flags.

Change log:

v8: Change PERF_BR_NONE to PERF_BR_UNKNOWN.

v7: Since the common branch type name is changed (e.g. JCC->COND),
    this patch is performed the modification accordingly.

v6: Move that multiline conditional code inside {} brackets.
    Move branch_type_stat_display() from builtin-report.c to
      branch.c.
    Move branch_type_str() from callchain.c to branch.c.

v5: It's a new patch in v5 patch series.

Signed-off-by: Yao Jin <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1500379995-6449-6-git-send-email-yao.jin@linux.intel.com
[ Don't use 'index' and 'stat' as names for variables, it shadows global decls in older distros ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>