Stmt: Introduce assert statement and related hooks

including two hooks called assertion_failure() and assertion_result() for
customization and tracking of assertion results.

testing/btest/language/assert-misc.zeek

@@ -0,0 +1,28 @@
+# @TEST-DOC: Test Describe() of assert statement. Expressions may be canonicalized.
+#
+# @TEST-EXEC: zeek -b %INPUT >out 2>&1
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+function test_function()
+	{
+	assert getpid() > 0;
+	}
+
+event zeek_init()
+	{
+	local f = function() {
+		assert getpid() > 0, fmt("my pid is funny: %s", getpid());
+	};
+	local g = function() {
+		assert to_count("42") == 42;
+	};
+
+	print "f", f;
+	f();
+
+	print "g", g;
+	g();
+
+	print "test_function", test_function;
+	test_function();
+	}