Fix compilation with latest rustc

[mre]

Some adjustments to make this crate work with the Rust 1.19.

Major changes:

• Some functionality (bitflags, num) has been removed from the standard library. Replaced the imports with the respective crates.
• Implement Clone for custom types
• Minor syntax changes in Rustlang
• Formatting using the latest rustfmt

Currently some unit tests are failing. This is due to expressions like compare(&mut machine, !128); in machine.rs. Before this was compare(&mut machine, -128); and I don't know what this means, really. Thought the - was negation, but seems like I'm mistaken. In any way, the second parameter is a usize, so does the - make sense here?

[mre]

Update: Replaced compare(&mut machine, -128); with compare(&mut machine, -128i8 as u8); thanks to the help on the rust irc channel. Still the unit tests fail.
Namely the failing tests are:

• machine::tests::add_with_carry_test
• machine::tests::compare_with_a_register_test
• machine::tests::compare_with_x_register_test
• machine::tests::compare_with_y_register_test
• machine::tests::decrement_memory_test
• machine::tests::subtract_with_carry_test

[mre]

Just noticed that all tests except for one will pass when I run the tests like this:

cargo test --release

The reason is that overflow checking is disabled then. Was this the intended behavior?

The only missing test failing in release mode is this:

thread 'machine::tests::decrement_memory_test' panicked 
at 'index out of bounds: the len is 2 but the index is 41394'

[mre]

Okay, I've fixed the remaining bug.
I've switched the byte slice for the memory to a vector (see here). The problem was that the initial allocation did not work. It was not allocating MEMORY_SIZE elements.

For some reason, the vec! syntax does not work. I've switched to this
.

Now all tests pass in release mode.

[mre]

All tests pass in debug now, too.
Used the explicit wrapping_add() and wrapping_sub() methods to allow overflow.
Alternatively I could have used std::num::Wrapping to achieve the same, but I found it more verbose.

[mre]

Just in case anyone is looking for a follow-up project, I forked this repo a while ago and a small group of people maintains it at https://github.com/mre/mos6502, so I think we can close this PR. Thanks for your initial work on the project. ❤️