Print stack trace on assert() failure or when calling fatal_error()

Note: this uses the __sanitizer_print_stack_trace() function from the
AddressSanitizer runtime, so it only works when AddressSanitizer is
in use.

xmalloc.c

@@ -1,21 +1,11 @@
-#include <assert.h>
 #include <errno.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>
-#include <syslog.h>
 #include "xmalloc.h"
-
-static NORETURN COLD void
-fatal_error(const char *msg, int err)
-{
-    syslog(LOG_ERR, "%s: %s", msg, strerror(err));
-    errno = err;
-    perror(msg);
-    abort();
-}
+#include "debug.h"
 
 static void *
 check_alloc(void *alloc)