[Patch 3/3] Separate `repeating` node from `alternative` node in regex

[Tim Shen]

Before this patch both alternative operator "|" and star operator "*"
generate _S_opcode_alternative node.

Now they generate _S_opcode_alternative and _S_opcode_repeat
respectively, because the alternative handing is simpler comparing to
the repeat node handling introduced by last patch.

The whole patch series are booted and tested, but this one is not
separately tested.

Thanks!


-- 
Regards,
Tim Shen