[phobos] array appending changes to druntime

[Walter Bright]

This TDPL book example still fails:

unittest {
int[] a = [0, 10, 20, 30, 40, 50, 60, 70];
auto b = a[4 .. $];
a = a[0 .. 4];
// At this point a and b are adjacent
a ~= [0, 0, 0, 0];
assert(b == [40, 50, 60, 70]); // passes; a got reallocated
}



because the agreed upon array append changes to druntime haven't been 
done yet. I can't recall who was doing that, or indeed if anyone had 
taken responsibility for getting it done.