libbeauty: Introduce strarray__strtoul_flags()

Counterpart of strarray__scnprintf_flags(), i.e. from a expression like:

   # perf trace -e syscalls:sys_enter_mmap --filter="flags==PRIVATE|FIXED|DENYWRITE"

I.e. that "flags==PRIVATE|FIXED|DENYWRITE", turn that into

   # perf trace -e syscalls:sys_enter_mmap --filter=0x812

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-8xst3zrqqogax7fmfzwymvbl@git.kernel.org


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