Fix BitVec on Big-Endian Systems about bitvec HOT 6 CLOSED

let bits = bitvec![0, 1, 0, 1, 1, 0, 1, 1, 0, 0,
                   0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
                   0, 0, 0, 0, 0, 0, 1, 1, 0, 0,
                   0, 1, 0, 1, 1, 0, 1, 1, 0, 0,
                   0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                   0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
                   0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

println!("{:?}", bits);
// BitVec<Lsb0, usize> [
//    0b0101101100000000110000000011000101011011000000001100000000110001,
//    0b000000,
//]

println!("0x1234u16.to_le_bytes()={:?}", 0x1234u16.to_le_bytes());
// 0x1234u16.to_le_bytes()=[52, 18]

let u16b = u16::from_ne_bytes(0x1234u16.to_le_bytes());
println!("u16b={:?}", u16b);
// u16b=13330

bytes[..16].store_le(u16b);
println!("bytes[..16]={:?}", bytes[..16]);
// ACTUAL:   bytes[..16]=BitSlice<Lsb0, u8> [01001000, 00101100]
// EXPECTED: bytes[..16]=BitSlice<Lsb0, u8> [00101100, 01001000]

let u16b = u16::from_ne_bytes(0x1234u16.to_ne_bytes());
bytes[..16].store_le(u16b);
assert_eq!(bytes[..16].load_le::<u16>(), 0x1234u16);

let bits: &BitSlice<Local, usize> = bits![1, 0, 1, 1, 0, 1, 0, 0, 1, 0];
println!("bits={:?}", bits);
// bits=BitSlice<Msb0, usize> [0000000000]