Fixes issue closing SyncTERM in curses mode on macOS.

Fixes issue reported from CCO BBS.

The native OS calls are ObjC, and the C/C++ APIs are being deprecated,
so we need something along these lines.  For now, I'm just moving the
path "stuff" in there since that's the bulk of the deprecation
warnings in building SyncTERM.

The issue was that the various semaphores and mutexes weren't being
initialized at all when sdl_initconio() wasn't called... so starting
the event thread and telling it to stop would access uncreated
semaphores and mutexes.

Split out the init, and be sure to call it before exiting.

1) Use static SDL since it's required by both conio and XPDev
2) Since the SDL thread will always run, any attempt to shut down
   the SDL thread calls exit(0).  Not exactly what we want to
   return, but at least this makes it not hang waiting for the
   impossible.

JSDoor only compiles one file that isn't shared with the sbbs3
target, so there's no need to build them all twice.

Should fix js test suite on darwin.

It builds and appears to run... not actually tested.

ircdcfg would not provide a valid irc.ini file

See merge request !426

Use the standard `extern char **environ' instead.
Fixes an issue with macOS.

Also, check that env is not NULL in js_init.

No real purpose to keeping the default min version at 10.9.

... much more still to do, I'm sure.

We need _CIOLIB_main on macOS... at least until the curses stuff works.

Eliminate some never-defined/used flags (copied from smb.html?)

Sorry Nightfox, this might break your scripts

e.g. stubs for JS command shells, examples of how to do file I/O, socket I/O
and such in Baja (which you really shouldn't).

Added type.js to replace type.src/bin

The JS file_area.user_dir is an object (not documented in jsobjs.html!) and
bbs.list_file_info() method expects the directory number (not object) as the
first argument. Reported by Jas Hud.

... when exporting from SMB to .msg ("stored message") file

This is a "newer" QWK control message supported by Synchronet (for like 20
years now), so it's been missing from the DOOR.ID file all this time and no
one noticed. <shrug>

This resolves the conflict with MSG_HOLD definition in socket.h on MacOS:
 /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/socket.h

And hey... [NET]MSG_HOLD isn't actually used anywhere? What's up with that.