Fix compiler warning: Size isn't 64 bits on 32 bit platforms.

Report by Peter Eisentraut.
Fix compiler warning.

Kevin Gritter reports that his compiler complains about inq and outq
being possibly-uninitialized at the point where they are passed to
shm_mq_attach().  They are initialized by the call to
setup_dynamic_shared_memory, but apparently his compiler is inlining
that function and then having doubts about whether the for loop will
always execute at least once.  Fix by initializing them to NULL.
test_shm_mq: Fix checks for negative queue size.

Noted while addressing compiler warnings pointed out on pgsql-hackers.
Fix missing parentheses resulting in wrong order of dereference.

This could result in referencing uninitialized memory.

Michael Paquier, in response to a complaint from Andres Freund
Logging running transactions every 15 seconds.

Previously, we did this just once per checkpoint, but that could make
Hot Standby take a long time to initialize.  To avoid busying an
otherwise-idle system, we don't do this if no WAL has been written
since we did it last.

Andres Freund
test_shm_mq: Try again to fix compiler warning.

Per complaints from Andres Freund and Tom Lane.
Fix whitespace
Suppress Coverity complaints in readfuncs.c.

Coverity is complaining that the value returned by pg_strtok in
READ_LOCATION_FIELD and READ_BITMAPSET_FIELD macros is not used. In commit
39bfc94c86f1990e9db8ea3da0e82995cc1b76db, we did this to the other macros
to placate compilers that complained when the variable was completely
unused, this extends that to the last remaining macros.