Make shift_ref and mut_shift_ref return Option instead of failing
Make pop_ref and mut_pop_ref return Option instead of failing on empty vectors
Make mut_last return Option instead of failing on empty vector (and add a test for mut_last)
Handle attributes on cross-crate tuple-structs correctly

Fixes #11741
Make next_power_of_two generic for unsigned integers

Also rename `next_power_of_two_opt` to `checked_next_power_of_two`.
Remove some unused imports
Remove free-standing div functions in std::uint
Move int and uint overflow tests into macros
auto merge of #11930 : bjz/rust/next_power_of_two, r=huonw
auto merge of #11932 : dmanescu/rust/11741-stability-cross-crate, r=alexcrichton

Fixes #11741
Added tests and removed xfail-fast from run-pass/simd-experimental which is now fixed (see #11738).
auto merge of #11944 : nathanielherman/rust/vec_opt, r=alexcrichton

Closes #11733