Today, user32:msg window update region tests may fail if there are
visible topmost windows in the current desktop, which conceals test
windows and thus affects update regions.

Fix this by introducing a temporary desktop to isolate fragile tests in.

Take a precaution to check for unexpected USER environment.  user32
tests are often hard to debug due to its graphical nature, especially in
batch WineTest runs.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55465
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55374
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54202
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=53891

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55505

GCC expects __stack_chk_fail() to be noreturn[1].  Returning from
__stack_chk_fail() can thus lead to subtle failures.

When crashing, use a volatile NULL pointer dereference.  Ideally we
would like to "abort()" here, but doing so would require two more
syscall definitions just for a cold function.  After all, the function
isn't even used at all if -fno-stack-protector is specified.

Also, don't say "stack smashing" (unlike glibc).  The preloader
currently initializes the stack canary value to a fixed value (0), which
serves little value in protecting against actual buffer overrun attacks.

[1]: https://gcc.gnu.org/onlinedocs/gcc-9.1.0/gccint/Stack-Smashing-Protection.html

Fixes: ac1761d1
Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55508

Both ISC_REQ_DELEGATE and ISC_RET_DELEGATE are properly translated
by the Unix side.
Signed-off-by: Dmitry Timoshkov <dmitry@baikal.ru>

Since most LDAP servers do not require mTLS, for now the callback
function is saved but not called.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=55507

Signed-off-by: Dmitry Timoshkov <dmitry@baikal.ru>

Stack pointer is randomized on Windows.