compiler/lang: add variadic function args support

compiler/tests/fn_variadic_test.v

@@ -0,0 +1,15 @@
+struct VaTestGroup {
+	name string
+}
+
+fn variadic_test_a(name string, groups ...VaTestGroup) {
+	assert groups.len == 2
+	assert groups[0].name == 'users' 
+	assert groups[1].name == 'admins'
+}
+
+fn test_fn_variadic() {
+	group1 := VaTestGroup{name: 'users'}
+	group2 := VaTestGroup{name: 'admins'}
+	variadic_test_a('joe', group1, group2)
+}