fix init, fix macOS globals, add macOS args, add args + parse_int example

[soxfox42]

Just a bunch of changes that came up while adding Callisto to my tak repo.

• rsp was being saved to rsi inside of __init instead of outside. This caused two issues. Linux libc argv handling was broken because rsi was overwritten before __x86_64_program_init, and Linux no-libc argv handling was broken because rsi was off by 8 bytes because of the __init return address.

  Because __x86_64_program_init is inlined anyway, I just removed the saved stack pointer and accounted for the offset manually. The alternative would be to save the stack pointer before call __init, but a different register would need to be used to avoid the first issue.

• Marked macOS core as supporting Args feature (implemented in std PR).

• Fixed globals failing to assemble on macOS due to use of absolute addressing.

  Most of this is accomplished with default rel, which tells NASM to use RIP-relative addressing wherever possible, but I also had to manually fix CompileAddr to generate lea + mov instead of just mov. This works fine on Linux too.

• Added add_args example. This is basically the program I used while testing Args on macOS and the parse_int function, and I figured it was a nice example to have.