* zig fmt
 * std.mem.join takes a slice of slices instead of var args
 * std.mem.join takes a separator slice rather than byte,
   and always inserts it. Previously it would not insert the separator
   if there already was one, violating the documented behavior.
 * std.mem.join calculates exactly the correct amount to allocate
   and has no call to allocator.shrink()
 * bring back joinWindows and joinPosix and the corresponding tests.
   it is intended to be able to call these functions from any OS.
 * rename std.os.path.resolveSlice to resolve (now resolve takes
   a slice of slices instead of var args)