pgsql: Fix a bunch of places that called malloc and friends with no NUL

Fix a bunch of places that called malloc and friends with no NULL check.

Where possible, use palloc or pg_malloc instead; otherwise, insert
explicit NULL checks.

Generally speaking, these are places where an actual OOM is quite
unlikely, either because they're in client programs that don't
allocate all that much, or they're very early in process startup
so that we'd likely have had a fork() failure instead.  Hence,
no back-patch, even though this is nominally a bug fix.

Michael Paquier, with some adjustments by me

Discussion: <CAB7nPqRu07Ot6iht9i9KRfYLpDaF2ZuUv5y_+72uP23ZAGysRg@mail.gmail.com>

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/052cc223d5ce1b727f62afff75797c88d82f880b

Modified Files
--------------
contrib/pg_standby/pg_standby.c               |  2 +-
contrib/vacuumlo/vacuumlo.c                   |  8 ++---
src/backend/bootstrap/bootstrap.c             | 14 +++-----
src/backend/port/dynloader/darwin.c           |  3 ++
src/backend/utils/misc/ps_status.c            | 27 +++++++++++++++
src/bin/pg_archivecleanup/pg_archivecleanup.c |  2 +-
src/bin/psql/command.c                        | 12 +++++--
src/common/exec.c                             |  9 +++--
src/test/isolation/isolationtester.c          | 14 ++++----
src/test/isolation/specparse.y                | 34 +++++++++----------
src/test/isolation/specscanner.l              |  4 +--
src/test/regress/pg_regress.c                 | 48 +++++++++++++--------------
12 files changed, 108 insertions(+), 69 deletions(-)