Handle pointee_align

[antoyo]

I noticed we don't handle pointee_align.

To implement this, look for pointee_align in cg_llvm and implement the same logic in cg_gcc.

[g4titanx]

hey @antoyo can you provide more context on this and i'd like to get on it as soon as possible
also, i'm yet to get a review on this pr: #586

[antoyo]

I added a bit more context in the top comment. Feel free to ask questions if you need more help.

I've been very busy these past weeks: I should be able to look at this PR by next week if it goes well.