[Ben: Ccing you on Bruno Haible's advice]
Having gone through the changes I needed to make to my sources to use the relocatable-lib-lgpl module, here's a list of things I think should be documented in doc/relocatable-maint.texi. If they're agreed to be correct, I'll prepare a documentation patch.
Makefile.am: the relevant CPPFLAGS should contain: -DENABLE_COSTLY_RELOCATABLE (if desired) and -DIN_LIBRARY.
Makefile.am: the relevant LIBADD variable, or equivalent, should contain
: A suitable invocation of AC_CONFIG_LIBOBJ_DIR([lib]) should be added.
Source: #include "relocatable.h"
Should automatic advice be also added to the module files to mention these when running gnulib-tool? (relocatable.h is already mentioned automatically).
Call set_relocation_prefix if desired. Not totally necessary (automatic initialisation code works on some platforms).
Additionally,configmake is useful to get a range of paths that it may be desired to relocate.
That's all I can see that I did; anything obvious that I've overlooked?
Additionally, I wonder about making -DENABLE_COSTLY_RELOCATABLE the default behaviour (the comments in relocatable.c say that the support is pretty cheap on most platforms).
Finally, how about making --enable-relocatable the default? The package I'm working on requires it, and again, if you've added relocation support, you might as well give it to users unless they want to turn it off.