[Patch] Add comments for future regex work

[Paolo Carlini]

On 12/02/2013 10:15 PM, Tim Shen wrote:
> ...for optimization purpose. Should be done in one month.
Great. Consider that we are now in Stage 3, until mid of February. 
Considering that <regex> is a new feature, I think we have some leeway 
in terms of timing, but definitely we can't commit invasive changes not 
fixing regressions while in Stage 4.

Thanks!
Paolo.