Jump the time forward (in 24-hour chunks) to find the next date/time the event will run rather than just adding 24-hours and assuming it's an event that runs every day (of the week or month) at a specific time.

Also, expose the next-run-date/time for an event as a new `next_run` property for `xtrn_area.event[]` (in `time_t` format) for easier debugging of these kinds of issues.
Also expose the error log level as a new property: `error_level` while we're here.

Closes #83, #108, #141.
Still to do: expose via JS (e.g. for use in msglist.js).

If either localtime_r() or mktime() return a error result, don't use use the
non-sensical time.
Nelgin has reported that under some conditions, he sees:
Your time has been reduced due to an upcoming event on Wed Dec 31 1969 18:00:00
when using Ctrl-T (time info hot key).
I don't have an explanation for this, but if either of those function calls
failed in getnextevent(), something like this could happen. <shrug>

- finduser() method no longer prints "Unknown user" upon failure (the calling
  script can do this if/when it wants).
- read_mail() method now accepts an optional 3rd argumnet (loadmail_mode)
  which may be used to load *only* un-read mail (for example), see LM_* in
  sbbsdefs.js

Pass the lm_mode as a 4th argument to any readmail mod (if one is installed) -
this correlates with the LM_* mode flag values (0 is normal/usual).

File attachments can also be in a file/####.out directory (e.g. outbound
Internet email attachments), so try deleting from there too when deleting
mail with attachments.

was never used. This was intended to be a method for internationalization,
letting the sysop change which key is used as the uiniversal "quit" key.
This commit replaces most of the uses of the hard-coded 'Q' for quit wtih the
3rd charcter in the text.dat YNQP string. Some hard-coded menus still have the
'Q' key hard-coded and will need to be addressed later. The text.h YN index
macro was changed to YNQP and the JS text index variable name will change
as well.

all exported functions and data types using a 32-bit time_t (time32_t).

inserting (long) typedefs to prevent warnings, but in the case of the JS File()
class, actually supporting file lengths > 32-bit.

timed event will execute in (default is any/all).

Remove time32str()

function.
sbbs_t::gettimeleft() is now using the C-exported gettimeleft() and
getnextevent() functions.

time-stamps.

Don't LOG negative time-left in gettimeleft().

event).

of the month.
now uses the even_time member variable instead of a local variable.
now create a log entry when time has been reduced due to upcoming event.
text.dat ReducedTime entry now may display the time the event will run.

variants (gmtime_r, localtime_r, and ctime_r) for thread-safe operation on Unix

GMT/UTC.

(no longer members of the C++ class sbbs_t).

Each function that requires a temp string variable, now has its own "tmp" local variable.