Needed for CIOLIB builds.

so define HAS_STDINT_H

The Linux lock() implementation in xpdev/filewrap.c requires that
_FILE_OFFSET_BITS is set to 64 or else OFD (sane) locks are not
used on Linux, defaulting back to the crazy per-process file region
locking of Linux of old. This was done in this commit:
http://cvs.synchro.net/commitlog.ssjs?99999#39639
because:
https://patchwork.kernel.org/patch/9289177/

but on 64-bit Linux, large file support is assumed and you don't
actually need to define _FILE_OFFFSET_BITS, we're peforming this
check for 32-bit Linuxes. Perhaps a check to see if sizeof(off_t)
== 8 would have been better. However, this change enables OFD
Locks for *all* flavors of Linux (not just 64-bit) - so that's
better.

Why do we care? Because using region locks on the same file in
a multi-threaded program doesn't really work right on Linux without
using OFD Locks. I saw this problem with receiving multiple
simultaneous emails in the mailserver and getting smb_locksmbhdr()
errors/failures when trying to save the message data or headers
of the one or more messages every time GitLab would send email
out to those whoe have opted-in to received email notifications
upon gitlab.synchro.net activity.

about redefining _XOPEN_SOURCE on every command-line (because pkt-config
is also defining it, to 600).

SDL audio should work from any thread, and on the platforms that care,
SDL video is coddled appropriately.
The only question is around SDL_Quit() in an audio-only build, but we
can punt on that since the default builds will never do that... the only
thing I'm aware of that could be broken that way is tone, which nobody
likes anyway.

any files), so use "del /q" instead.

deprecated

Prepare for upcoming "hash" library.

about undeclared functions (vasprintf and pthread_setname_np) when building
sbbs3.

(points to lib and include files in 3rdp/win32.release/sdl).

SBBSCTRL is set. Also changed the library versioning from 3.16 to 3.17.

in WinSock (wsock32.lib), but might add the IP Helper lib or other cfg
properties later.

on Windows XP now.  At the very least, it will now require MSVCR80.DLL.

warnings when a string or character literal contains invalid UTF-8.

is 'clang'

This will also enable SVID stuff, but that appears to be unavoidable.

See the following URIs:
https://lwn.net/Articles/590381/
https://sourceware.org/glibc/wiki/Release/2.20#Deprecation_of__BSD_SOURCE_and__SVID_SOURCE_feature_macros
http://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html#index-_005fDEFAULT_005fSOURCE

be set and read using the POSIX macros and related (currently Linux-only).

of the compiler (icc, gcc, and clang supported).

headers are rife with.  Re-enables cross-building with mingw32 (at least for
SyncTERM).

POSIX for stdio and more.
BSD because BSD is awesome.
X/Open for timezone.

except for the ISO C ones are disabled.  Since we use POSIX, BSD, and SYSV
APIs, define _GNU_SOURCE which re-enables them all.

Only for Linux so far.

Yay!

(don't assume SSE support in target CPU).

Shouldn't be used though.