This patch was technically backported from a later version of
MineClone2. Between the point where Mineclonia forked, and the point
where this patch was developed, MineClone2 introduced a "mcl_colors"
mod which, presumably just lists some colors. This commit removes
references to that mod, as it doesn't exist in our history.
A preview of a crafted banner is now shown next to the craft result box
to help players visualize what they're crafting. Due to the formspec
version, the preview can't be shown over top of the actual result slot.
A utility function (mcl_banners.get_overlay) is added to generate
formspec-able texture strings for arbitrary banners.