PPC: Detect unpooled string literal references

[LagoLunatic]

objdiff already supports detected pooled PPC strings (@stringBase), this PR adds support for unpooled ones as well:

It assumes that a data symbol is an unpooled string if it's at least 2 bytes long and it contains exactly 1 null byte at the end of the symbol. I didn't check that all the bytes are displayable ASCII characters because I didn't want to exclude non-ASCII strings. This might have false positives but I haven't run into any in testing yet.

[encounter]

Suggested change

	if bytes.len() >= 2 && bytes.iter().position(|&c| c == b'\0') == Some(bytes.len() - 1) {
	if bytes.len() >= 2 && bytes.iter().position(|&c| c == b'\0') == bytes.last() {

I think this should work

[LagoLunatic]

last would return the last byte in the slice, I think? This is comparing to the last index (len-1), not the value, since all the values were already read inside the loop.

The compiler also doesn't like last for some reason:

can't compare `std::option::Option<usize>` with `std::option::Option<&u8>`
the trait `PartialEq<std::option::Option<&u8>>` is not implemented for `std::option::Option<usize>`
but trait `PartialEq<deranged::OptionRangedUsize<_, _>>` is implemented for it
for that trait implementation, expected `deranged::OptionRangedUsize<_, _>`, found `std::option::Option<&u8>`

[encounter]

I think my brain was melted by C++ iterators, nevermind

[encounter]

Doesn't have to be this PR, just thinking aloud, this logic could easily live in common arch code.

[encounter]

Thanks!