proc: whitespace fixes
proc: better error check in proc_foreach

When reading the proc dir, filenames are parsed as PIDs using strtoul(),
without any error checking.  Now we check for filenames which are not
formatted as we expect and emit a syslog rather than plough ahead and
attempt to parse the *directory* as a file.
proc: avoid accidentally reading proc directory

as if it were a proc file.  There's no good that can come of that.
proc: handle empty/bogus proc files

without crashing in proc_foreach_helper().
proc: create & update proc files atomically

without leaving them in an empty or partially correct state on disk for
another process to attempt to read using proc_foreach().
Revert "master: remove Service.family"

This reverts commit 2747cebc24581806382ae83fb8cef92591c67151.

It is used by SNMP
ltmpd: whitespace fixes
lmtpd: use xmalloc
imapd: whitespace fixes
pop3d: whitespace fixes
pop3d: use xmalloc
mboxevent: whitespace fixes
telemetry: whitespace fixes
cunit: handle libSASL API change

The auxprop plugin API changed, and this code depends on it.  Handle
both the old and new APIs using an ifdef.
cunit: don't ignore return value from system()

Because -Wall -O2 complains about it.
imapd: use xmalloc
Don't ignore the return from strtoul()

Because -Wall -O2 complains about it.
Initialise various auto variables

Because -Wall -O2 complains about it.  Even when the values cannot
possibly be used uninitialised.
mboxevent: remove an unused goto label

Because -Wall -O2 complains about it.
Don't ignore the return from write()

Because -Wall -O2 complains about it.  And it's actually potentially
useful.