[PATCH]: Doc fixes related to GC and UnionVal

[jrtayloriv]

I made some edits to docs/memory_internals.pod and to docs/pdds/pdd28_strings.pod to remove references to Unionval, and bring the state of the documentation closer to the current implementation.

I also added some minor fixes for some invalid references to src/cpu_dep.c in the in-code documentation.

[jrtayloriv]

Added an additional reference in pdd09_gc.pod to the paper "Uniprocessor Garbage Collection Techniques", a very useful intro to GC, which is freely available online.

[jkeenan]

Replying to jrtayloriv:

Added an additional reference in pdd09_gc.pod to the paper "Uniprocessor Garbage Collection Techniques", a very useful intro to GC, which is freely available online.

Re second patch (pdd09_gc.pod--patch):

"Uniprocessor Garbage Collection Techniques"
ftp://ftp.cs.utexas.edu/pub/garbage/gcsurvey.ps

Is this available in a document format other than PostScript and reachable by http?

I believe this would make the document more easily available to our readers.

Thank you very much.

kid51

[jrtayloriv]

additional patch to pdd09 -- add ref to GC paper

[jrtayloriv]

done and done

[chromatic]

Thanks, applied as r40935.