string: test i64() and u64()

vlib/builtin/string.v

@@ -206,7 +206,7 @@ pub fn (s string) u32() u32 {
 
 pub fn (s string) u64() u64 {
 	$if tinyc {
-		return u64(s.int()) // TODO
+		return u64(s.i64()) // TODO
 	} $else {
 		return C.strtoull(*char(s.str), 0, 0)
 	}

vlib/builtin/string_test.v

@@ -276,6 +276,7 @@ fn test_arr_contains() {
 fn test_to_num() {
 	s := '7'
 	assert s.int() == 7
+	assert s.u64() == 7
 	f := '71.5 hasdf'
 	assert f.f32() == 71.5
 	b := 1.52345
@@ -285,6 +286,9 @@ fn test_to_num() {
 	a = '${num:03d}'
 	vals := ['9']
 	assert vals[0].int() == 9
+	big := '93993993939322'
+	assert big.u64() == 93993993939322
+	assert big.i64() == 93993993939322
 }
 
 fn test_hash() {
@@ -477,3 +481,4 @@ fn test_escape() {
 	//a := 10
 	//println("\"$a")
 }	
+