Currently we have recipes to build both postgresql 9.1 and 9.2 (see
9f1f0759 "provide both postgres 9.1 and 9.2") which mostly duplicate
each other with minor difference that 9.1 is built with perl and 9.2
without (perl added to 9.1 in dbbd9a96 "Include Perl in Postgres").

To reduce the duplication let's move common compilation bits to common
section.

NOTE I've tried to add perl to postgresql 9.2 as well and got the
following compilation error:

    ld: .../perl/libs-c/libperl.a(op.o): relocation R_X86_64_32 against `.rodata.str1.8' can not be used when making a shared object; recompile with -fPIC
    .../parts/perl/libs-c/libperl.a: could not read symbols: Bad value

which happens because libperl.a is not compiled with fPIC.

For now we don't need perl in postgresql92 and this is not handled, and
we just deduplicate building recipes without any actual change for
resulting commands how the software is built.

component/postgresql/buildout.cfg defines both postgresql92 and
postgresql sections, with postgresql being just

    [postgresql]
    <= postgresql92

On the other hand, software/postgresql uses postgresql92 in parts, but
bin = ${postgresql:location}/bin in instance, which leads to _both_
postgresql and postgresql92 being built, and postgresql92 not used at all.

Let's fix it and use postgresql everywhere.

/cc @kazuhiko

/reviewed-by @kazuhiko  (on !21)

Commit 6f009a9f broke generation of zope-*.conf

Partition root should be used to control overall permissions, which is
typically a safe-enough 0750 (depending on slapformat and sysadmin).
umask is applied at libc mkdir level, so this typically results in 0755
actual permission.
More restrictive permissions should only be used when really needed.

/reviewed-by @kazuhiko

This is a follow-up of commit 6f009a9f

Conflicts:
	stack/slapos.cfg

NEO is still in heavy development and it must be easy to update code on
existing deployment.

Zope integrated Products.signalstack back in 2010:

    https://github.com/zopefoundation/Zope/commit/16796274
    ( Integrated the Products.signalstack / z3c.deadlockdebugger
      packages. You can now send a SIGUSR1 signal to a Zope process and get a
      stack trace of all threads printed out on the console. This works even
      if all threads are stuck. )

In 404150b7 (wendelin: Teach -dev build to dump all threads traceback on
SIGUSR1) it was my mistake to add Products.signalstack.

/reviewed-by TrustMe
/cc @Tyagov

This fixes the following random failures:

While:
  Installing slapos-deps-eggs.
  Getting distribution for 'ZODB3==3.10.5+SlapOSPatched001'.

An internal error occurred due to a bug in either zc.buildout or in a
recipe being used:
Traceback (most recent call last):
  ...
  File "zc/buildout/easy_install.py", line 968, in _get_dist
    shutil.copytree(dist.location, newloc)
  File "shutil.py", line 177, in copytree
    os.makedirs(dst)
  File "os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 17] File exists: '.../eggs/ZODB3-3.10.5-py2.7-linux-x86_64.egg'