Limiting history size seems to be implemented inefficiently

[Janek Warchoł]

Hello,

I may be wrong, but from what I see in
lib/readline/history.c:stifle_history, every time stored history reaches
HISTSIZE limit, the whole array keeping history data is rewritten (by
moving each element one index further to make room for new entry. This is
quite inefficient. Shouldn't we rather have a "0th_index" variable
remembering where in the array the first element is and manipulate it?

Let me know if it's not clear what I mean and I'll elaborate.

best,
Jan