Move pgfnames() from libpgport to libpgcommon

It requires pstrdup() from libpgcommon.
Move rmtree() from libpgport to libpgcommon

It requires pgfnames() from libpgcommon.
Add *.pot to .gitignore
Add libpgcommon to backend gettext source files

This ought to have been done when libpgcommon was split off from
libpgport.
Consistently use unsigned arithmetic for alignment calculations.

This avoids an assumption about the signed number representation.  It is
anticipated to have no functional changes on supported configurations;
many two's complement assumptions remain elsewhere.

Per a suggestion from Andres Freund.
doc: Improve setup for documentation building with FOP

Add a makefile rule for building PDFs with FOP.  Two new build targets
in doc/src/sgml are postgres-A4-fop.pdf and postgres-US-fop.pdf.

Run .fo output through xmllint for reformatting, so that errors are
easier to find.  (The default output has hardly any line breaks, so you
might be looking for an error in column 20000.)

Set some XSLT parameters to optimize for building with FOP.

Remove some redundant or somewhat useless chapterinfo/author
information, because it renders strangely with the FO stylesheet.

Reviewed-by: Álvaro Herrera <alvherre@2ndquadrant.com>
Extend cube on-disk format to pack points more tightly.

If the lower left and upper right corners of a cube are the same, set a
flag in the cube header, and only store one copy of the coordinates. That
cuts the on-disk size into half for the common case that the cube datatype
is used to represent points rather than boxes.

The new format is backwards-compatible with the old one, so pg_upgrade
still works. However, to get the space savings, the data needs to be
rewritten. A simple VACUUM FULL or REINDEX is not enough, as the old
Datums will just be moved to the new heap/index as is. A pg_dump and
reload, or something similar like casting to text and back, will do the
trick.

This patch deliberately doesn't update all the alternative expected output
files, as I don't have access to machines that produce those outputs. I'm
not sure if they are still relevant, but if they are, the buildfarm will
tell us and produce the diff required to fix it. If none of the buildfarm
animals need them, they should be removed altogether.

Patch by Stas Kelvich.
Fix blatantly broken record_image_cmp() logic for pass-by-value fields.

Doesn't anybody here pay attention to compiler warnings?
Adjust cube.out expected output for new test queries.

Previous commit modified the test case, but I didn't update cube.out
expected output file in previous commit because it was not needed by the
platforms I have easy access to. Buildfarm animal 'dugong', running
"Debian 4.0 icc 10.1.011 ia64", has now gone red because of that, so update
it now.

Also adjust cube_3.out. According to git history, it was added to support
64-bit MinGW. There is no such animal in the buildfarm, so I'm doing this
blindly, but it was added quite recently so maybe someone still cares.
Make use of psprintf() in recent changes
Get rid of use of asprintf() in favor of a more portable implementation.

asprintf(), aside from not being particularly portable, has a fundamentally
badly-designed API; the psprintf() function that was added in passing in
the previous patch has a much better API choice.  Moreover, the NetBSD
implementation that was borrowed for the previous patch doesn't work with
non-C99-compliant vsnprintf, which is something we still have to cope with
on some platforms; and it depends on va_copy which isn't all that portable
either.  Get rid of that code in favor of an implementation similar to what
we've used for many years in stringinfo.c.  Also, move it into libpgcommon
since it's not really libpgport material.

I think this patch will be enough to turn the buildfarm green again, but
there's still cosmetic work left to do, namely get rid of pg_asprintf()
in favor of using psprintf().  That will come in a followon patch.
Replace pg_asprintf() with psprintf().

This eliminates an awkward coding pattern that's also unnecessarily
inconsistent with backend coding.  psprintf() is now the thing to
use everywhere.
Suppress a couple of compiler warnings seen with older gcc versions.

To wit,
bgworker.c: In function `RegisterDynamicBackgroundWorker':
bgworker.c:761: warning: `generation' might be used uninitialized in this function
dsm_impl.c: In function `dsm_impl_op':
dsm_impl.c:197: warning: control reaches end of non-void function

Neither of these represent actual bugs, but we may as well tweak the code
so that more compilers can tell that.  This won't change the generated code
on compilers that do recognize that the cases are unreachable.