Add about 60 more DOCDOC comments to 0.2.3

Also, try to resolve some doxygen issues.  First, define a magic
"This is doxygen!" macro so that we take the correct branch in
various #if/#else/#endifs in order to get the right documentation.
Second, add in a few grouping @{ and @} entries in order to get some
variables and fields to get grouped together.