Prevent closing of unrelated handles

If our `shmget()` fails for certain reasons, the segment handle is
closed.  However, the handle might be reused by Windows, and as such we
must not close it again when shutting down the TSRM.

Closes GH-15984.

NEWS

@@ -30,6 +30,9 @@ PHP                                                                        NEWS
   . Fixed bugs GH-15908 and GH-15026 (leak / assertion failure in streams.c).
     (nielsdos)
 
+- TSRM:
+  . Prevent closing of unrelated handles. (cmb)
+
 - XML:
   . Fixed bug GH-15868 (Assertion failure in xml_parse_into_struct after
     exception). (nielsdos)

TSRM/tsrm_win32.c

@@ -707,6 +707,7 @@ TSRM_API int shmget(key_t key, size_t size, int flags)
 	if (NULL != shm->descriptor && (shm->descriptor->shm_perm.key != key || size > shm->descriptor->shm_segsz)) {
 		if (NULL != shm->segment) {
 			CloseHandle(shm->segment);
+			shm->segment = INVALID_HANDLE_VALUE;
 		}
 		UnmapViewOfFile(shm->descriptor);
 		shm->descriptor = NULL;