Handle vector reallocations in yiqi::commandline::NullTermArray::append

If firstStoredNewStrings gets reallocated then all of the pointers
that were stored in vector will be invalidated, so we need to refresh
all of them

Fixes #37
Merge pull request #41 from smspillaz/yiqi.item_31

Handle vector reallocations in yiqi::commandline::NullTermArray::append