Change definition for the ChoiceString IsString.
Change definition for the ChoiceString IsString.

This is not faster than the previous solution, a bit to
my suprise.

mikehat/blaze-all,dylex/blaze-markup,mikehat/blaze-all,iblech/blaze-html,iblech/blaze-html,mikehat/blaze-all,jgm/blaze-html,jgm/blaze-html,Soostone/blaze-markup-haste,FranklinChen/blaze-markup,dylex/blaze-markup,Soostone/blaze-html-haste,Soostone/blaze-markup-haste,FranklinChen/blaze-markup,jgm/blaze-html