Need to declare "Stringy" data

[m4b]

Can hack this right now (in new branch) by doing:

    // ld.gold: warning: deadbeef.o: last entry in mergeable string section '.data.DEADBEEF' not null terminated
    obj.declare("DEADBEEF", Decl::Data { local: false })?;

But this is kind of a hack; also we should properly set the alignment of the section to 1 for strings, and Ctx::size() otherwise for starters.

[m4b]

done in #22