useless LIMIT_OPTION_DEFAULT

Hi, all

By reading the codes, I found that we process limit option as LIMIT_OPTION_WITH_TIES when using WITH TIES
and all others are LIMIT_OPTION_COUNT by  commit 357889eb17bb9c9336c4f324ceb1651da616fe57.
And check actual limit node in limit_needed().
There is no need to maintain a useless default limit enum. 
I remove it and have an install check to verify.

Are there any considerations behind this?
Shall we remove it for clear as it’s not actually the default option.