* README.rpm-dist.template: Mainly automatize generation of the
help for 'MULTIPLE POSTMASTERS' scenario.  Fix other sysv/systemd
nuances.
* TODO: Mention some TODOs.

The benefit is that sgml format we write does not need to be kept
formated precisely.  The output format still needs some "style"
fixes, but now docbook2txt is able to generates correct text-file
README.rpm-dist without problems on RHEL 5.10+.

* .gitignore: Added all intermediate files of README file.
* Makefile.am: Generated README file is firstly filtered through
$(SED_RULES), then macros are expanded by m4 and then docbook2txt
is called.
* README: Document subset of dependencies.
* README.rpm-dist.in: Move to ...
* README.rpm-dist.template: ... here, with docbook transformation.
* TODO: Document we should should work docbook docs.
* configure.ac: AC_SUBST also WANT_SYSVINIT.

Turns out we need to support upgrade from more than one previous
database versions.  The plan is to make this as general as easily
possible, "run-time" configurable without need to recompile.

* postgresql-setup.in: Add options --upgrade-from and
--upgrade-ids.  Require root access (as late as possible).
($USAGE_STRING): Adjust help output accordingly.
($PGMAJORVERSION, $PREVMAJORVERSION)
($PREVPGENGINE): Remove newly useless globals.
($option_upgradefrom): New option default.
(set_var, root_prereq): New helper functions.
(parse_upgrade_setup): Helper function to parse upgrade
configuration.
(print_version): Don't print PREVMAJORVERSION as it is (with
configuration) useless.
(upgrade): Create new $inplace local to handle in-place and
copy-like migrations differently.  Use the variable set generated
by parse_upgrade_setup() function.  Small err message fixes.
(handle_service_env, handle_pgconf): Remove the MODE argument.
(parse_configuration): Generalize operations which needed to be
done on two places.
* upgrade_config.template: Example of ./configure time config
file.  Based on files like this the run-time is generated.
* share/postgresql-setup/.gitignore: New file.
* share/postgresql-setup/Makefile.inc: New file.
* build-helpers/build-config: New file, generator of configuration
files.
* build-helpers/Makefile.inc: New file.
* Makefile.am: Distribute upgrade_config.template.  Start the
conversion to flat Makefile and include two new Makefile.inc
snippets.
* configure.ac: New --with-upgrade-config option.  Propagate the
rawpkgdatadir and UPGRADE_CONFIG_LIST variables into Makefile.
(INSTANTIATE): Enhance to create the leading path also.
(INSTANTIATE_CONV): Convenience helper for leading path of target
creation.
* auxdir/install_local: New (just-for-git) installation helper.
* .gitignore: Don't hide share/postgresql-setup.
* TODO: Mention that KDE folks would like to migrate somehow.

* postgresql-check-db-dir.in: Just fix typos.
* postgresql-setup.in: Reorganize --help.
* TODO: Adjust after some time.

.. only when '--unit=postgresql'.  When user specifies
--unit=postgresql@unitname, the --port is still required.

Also, don't adjust the 'port = ' configuration in postgresql.conf
when not necessary.

Also generate files using sed as is suggested by autoconf manual
(and the autoconf project does so internally).