pgsql: Provide and use a makefile target to build all generated headers

Provide and use a makefile target to build all generated headers.

As of 9.6, pg_regress doesn't build unless storage/lwlocknames.h has been
created; but there was nothing forcing that to happen if you just went into
src/test/regress/ and built there.  We previously had a similar complaint
about plpython.

To fix in a way that won't break next time we invent a generated header,
make src/backend/Makefile expose a phony target for updating all the
include files it builds, and invoke that before building pg_regress or
plpython.  In principle, maybe we ought to invoke that everywhere; but
it would add a lot of usually-useless make cycles, so let's just do it
in the places where people have complained.

I made a couple of cosmetic adjustments in src/backend/Makefile as well,
to deal with the generated headers in consistent orders.

Michael Paquier and Tom Lane

Report: <31398.1467036827@sss.pgh.pa.us>
Report: <20150916200959.GB32090@msg.df7cb.de>

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/548af97fcec5543603c20b61fec60f8147a05b29

Modified Files
--------------
src/Makefile.global.in       |  9 ++++++++-
src/backend/Makefile         | 30 ++++++++++++++++++------------
src/pl/plpython/Makefile     | 10 +++++-----
src/test/modules/Makefile    |  5 +----
src/test/regress/GNUmakefile |  4 ++--
5 files changed, 34 insertions(+), 24 deletions(-)