Add POSIX 2024 NSIG_MAX.

https://www.austingroupbugs.net/view.php?id=741

Change-Id: I89117528e1ed8ab0f922bfa394fab16003070eab
diff --git a/tests/limits_test.cpp b/tests/limits_test.cpp
index bc13a3f..64d9a33 100644
--- a/tests/limits_test.cpp
+++ b/tests/limits_test.cpp
@@ -78,3 +78,11 @@
 #error ULLONG_MAX
 #endif
 }
+
+TEST(limits, highest_signal_plus_one) {
+#if defined(__BIONIC__)
+  ASSERT_EQ(65, NSIG_MAX);
+#endif
+  ASSERT_EQ(65, NSIG);
+  ASSERT_EQ(65, _NSIG);
+}