reinstate infinite-sky

[ab9rf]

infinite-sky extends the map block array, but the siege update added a fairly large number of objects (plot_invasion_mapsts) containing pim_blockst objects that must be conformal with the main map block array; thus, if we change the size of the map block array we have to resize all of these objects. there are a lot of plot_invasion_mapst objects - there is one in plotinfo as well as potentially one in every entityst, and so when infinite-sky resizes the current site map it also has to resize all of the plot_invasion_mapsts referencing this site so that lookups in the block index in these invasion maps will not cause undefined behavior