manual: sprinkle with some calls to MESSAGE
manual: faq: add entry about the relocatable toolchain
manual: faq: add workaround to avoid rebuilding the buildroot toolchain after
each clean
manual: minor fix in patch-policy.txt
manual: misc. post-{build,image} scripts fixes

* update post-build scripts mechanism that now support several scripts
* fix formatting
manual: update {deprecated,package}-list.txt

* add the gen-manual-lists.py script generating the target and host
  package tables, and the deprecated stuff list as well. These tables
  and lists are generated parsing the Config.in files;
* add a make target to update these lists in the manual;
* update the these appendices of the manual.
Makefile: add to the release target a warning about the manual updates.

The manual-update-lists target is not added to the dependencies of the
release target to allow editing the generated files.