It's not been added to R, because no one thought it was important enough to add to R.
SPSS seems to have taken a scattergun approach to post hoc tests - they've just kept adding them. Stuff that appears in (say) SPSS is based on marketing, rather than need. SPSS thinks that they can say "We have more post hoc tests than SAS, Stata and Statistica put together, so you should buy our software". One rarely sees these tests mentioned outside the context of SPSS (and rarely outside the context of books that try to cover everything in a particular SPSS function). A slight problem with that book is that it's a rewrite of a book that was written for SPSS, and so sometimes a different structure would be sensible, so that it matched R, not SPSS.
For R, if someone cared enough to put it in, someone will have put it in. The fact that people have found the time to write thousands of packages for R, and none of them included (say) the Hochberg GT2 test might be telling us something.
If you really must do these post hoc tests (I'm not a fan, and rarely do them), I guess you have two choices:
You could bootstrap it.
You could write it yourself. The algorithms that SPSS uses are publised here: ftp://public.dhe.ibm.com/software/analytics/spss/documentation/statistics/20.0/en/client/Manuals/IBM_SPSS_Statistics_Algorithms.pdf
Also, note that this issue came up several years ago on the R help list (I suspect they'd read the same book), https://stat.ethz.ch/pipermail/r-help/2005-November/083595.html