Add copy(::AESBlock)

[martinholters]

Either this or an implementation of unaliascopy is needed if a proper dataids is added, as JuliaLang/julia#26237 proposes. I don't see any reason not to specialize copy like this here. (Without this, a Vector{UInt8} is returned.)

I didn't know where to add tests. They should probably look something like

a=AES.AESBlock(rand(UInt8, 100), 3)
ac=copy(a)
@test ac == a
@test ac !== a
@test ac isa AES.AESBlock

[kanav99]

Thank you @martinholters ! I have added the tests. I have been inactive on this repository, but if you think you need some more features, do let me know, I plan on extending the functionality.

[martinholters]

I only came here from looking at the failures in JuliaLang/julia#26237, I'm not actually using your package for anything (yet)---sorry. Although it just so happens that I give a course in croptography...

[kanav99]

Ohh awesome, no worries!