pgsql: Don't generate plain-text HISTORY and src/test/regress/README an

Don't generate plain-text HISTORY and src/test/regress/README anymore.

Providing this information as plain text was doubtless worth the trouble
ten years ago, but it seems likely that hardly anyone reads it in this
format anymore.  And the effort required to maintain these files (in the
form of extra-complex markup rules in the relevant parts of the SGML
documentation) is significant.  So, let's stop doing that and rely solely
on the other documentation formats.

Per discussion, the plain-text INSTALL instructions might still be worth
their keep, so we continue to generate that file.

Rather than remove HISTORY and src/test/regress/README from distribution
tarballs entirely, replace them with simple stub files that tell the reader
where to find the relevant documentation.  This is mainly to avoid possibly
breaking packaging recipes that expect these files to exist.

Back-patch to all supported branches, because simplifying the markup
requirements for release notes won't help much unless we do it in all
branches.

Branch
------
REL9_0_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/e1e7642bd3bdde980c481c5feb7739c4f841f757

Modified Files
--------------
GNUmakefile.in                       |    4 +--
HISTORY                              |    6 ++++
README                               |    3 +-
README.git                           |   12 +++----
doc/src/sgml/.gitignore              |    4 ---
doc/src/sgml/Makefile                |   21 +++---------
doc/src/sgml/docguide.sgml           |   21 ++++--------
doc/src/sgml/generate_history.pl     |   58 ----------------------------------
doc/src/sgml/release.sgml            |    5 +--
doc/src/sgml/standalone-install.sgml |   16 +---------
src/test/regress/README              |    3 ++
src/tools/RELEASE_CHANGES            |    1 -
12 files changed, 30 insertions(+), 124 deletions(-)