sort: fix C compilation error for fn abc(mut a []int) { a.sort() }

vlib/builtin/sorting_test.v

@@ -0,0 +1,40 @@
+const (
+	unsorted = [2,30,10,20,1]
+	sorted_asc = [1, 2, 10, 20, 30]
+	sorted_desc = [30, 20, 10, 2, 1]
+)
+
+fn test_sorting_simple() {
+	mut a := unsorted
+	a.sort()
+	eprintln(' a: $a')
+	assert a == sorted_asc
+}
+
+fn test_sorting_with_condition_expression() {
+	mut a := unsorted
+	a.sort(a>b)
+	eprintln(' a: $a')
+	assert a == sorted_desc
+}
+
+
+fn mysort (mut a []int) {
+	a.sort()
+}
+
+fn test_sorting_by_passing_a_mut_array_to_a_function() {
+	mut a := unsorted
+	mysort(mut a)
+	eprintln(' a: $a')
+	assert a == sorted_asc
+}
+
+/*
+fn test_sorting_by_passing_an_anonymous_sorting_function() {
+	mut a := unsorted
+	a.sort(fn(a &int, b &int) int {	return *b - *a })
+	eprintln(' a: $a')
+	assert a == sort_desc
+}
+*/