Fix OpPlus outputting zero-length repetitions
Fix OpPlus outputting zero-length repetitions

Was not adding min to the size of repeated strings under OpPlus and
OpStar. This is accidentally fine for OpStar, as min is always 0, but
OpPlus would end up limiting its result length by 1 and not having
a minimum output of 1 rune.

Change-Id: I1683cebfe4d08efce16319435c178f2dcc2bc6c7

nilium/regen