stage2: concat/mult of slices should yield a ptr to an array

[topolarity]

hundo p for test/behavior/slice.zig

[topolarity]

Before fixing, this test failure showed a src loc in the wrong file (thanks to @mitchellh for the heads up):

/home/topolarity/repos/zig/stage2/lib/zig/std/mem.zig:548:45: error: expected []const u8, found [8]u8
    try testing.expect(lessThan(u8, "abcd", "bee"));
                                            ^

I plan to try to fix that up in another PR soon

[andrewrk]

I'd like to re-evaluate this as part of the language spec - this test precedes the changes from #863 which made slices with comptime-known start and end indexes return single-pointers to arrays instead of slices. In light of this I think the test cases should perhaps be changed to have ++ and ** always return single-pointers to arrays.

What do you think?

[topolarity]

Works for me! Updated with the new behavior 👍