perf evsel: Allow passing a left alignment when printing a symbol

For callchains, etc where we want it to align just below the syscall
name, for instance, in 'perf trace'

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-uk9ekchd67651c625ltaur5y@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>