Cap recursion in igbinary_unserialize_zval at BG(unserialize_max_depth)
(default 4096, 0 disables) on PHP 7.4+, hardcoded 4096 on 7.0-7.3.
Without the cap, a deeply nested payload exhausts the C stack and
segfaults the worker, reachable via session.serialize_handler=igbinary
before userland code runs.

Mark igbinary_unserialize_zval zend_always_inline so the per-zval
depth check folds into each callsite, restoring the pre-cap stack-
frame profile on the unserialize hot path. Reorder the guard to
short-circuit on the dynamic counter first and use ZEND_LONG_FMT
for the warning so the value isn't silently truncated to 32 bits
when zend_long is 64-bit and long is 32-bit (Windows x64).

ZEND_LONG_FMT expands to "%" PRId64 / PRId32 from <inttypes.h>; older
PHP Windows builds didn't pull that header transitively, so the warning
in igbinary_unserialize_zval failed to compile with "missing ')' before
PRId64". Include inttypes.h directly. The depth-bomb test built a
250 KB payload with a 50000-iteration .= loop (O(n^2) in PHP), which
took longer than the 6h CI timeout under valgrind on PHP 8.0+. Build
the same payload via str_repeat with 5000 levels instead.