pgsql: Switch the semaphore API on Solaris to unnamed POSIX.

Switch the semaphore API on Solaris to unnamed POSIX.

Solaris descendants (Illumos, OpenIndiana, OmniOS, etc.) hit System V
semaphore limits ("No space left on device" from semget) when running
many parallel test scripts under default system settings.  We could
tell people to raise those settings, but there's a better answer.
Unnamed POSIX semaphores have been available on Solaris for decades
and work well, so prefer them, as was recently done for AIX.

This patch also updates the documentation to remove now-unnecessary
advice about raising project.max-sem-ids and project.max-msg-ids.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Greg Burd <greg@burd.me>
Discussion: https://postgr.es/m/470305.1772417108@sss.pgh.pa.us

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/0123ce131fca454009439dfa3b2266d1d40737d7

Modified Files
--------------
doc/src/sgml/runtime.sgml | 9 ++-------
meson.build               | 1 +
src/template/solaris      | 5 +++++
3 files changed, 8 insertions(+), 7 deletions(-)