builtin: add charptr str() and change string format (#12973)

vlib/builtin/int.v

@@ -391,14 +391,18 @@ pub fn (nn int_literal) hex() string {
 // hex returns the value of the `voidptr` as a hexadecimal `string`.
 // Note that the output is ***not*** zero padded.
 pub fn (nn voidptr) str() string {
-	return u64(nn).hex()
+	return '0x' + u64(nn).hex()
 }
 
 // hex returns the value of the `byteptr` as a hexadecimal `string`.
 // Note that the output is ***not*** zero padded.
 // pub fn (nn byteptr) str() string {
 pub fn (nn byteptr) str() string {
-	return u64(nn).hex()
+	return '0x' + u64(nn).hex()
+}
+
+pub fn (nn charptr) str() string {
+	return '0x' + u64(nn).hex()
 }
 
 pub fn (nn byte) hex_full() string {

vlib/builtin/int_test.v

@@ -29,12 +29,14 @@ fn test_str_methods() {
 	assert u32(-1).str() == '4294967295'
 	assert u64(1).str() == '1'
 	assert u64(-1).str() == '18446744073709551615'
-	assert voidptr(-1).str() == 'ffffffffffffffff'
-	assert voidptr(1).str() == '1'
+	assert voidptr(-1).str() == '0xffffffffffffffff'
+	assert voidptr(1).str() == '0x1'
 	assert (&byte(-1)).str() == 'ffffffffffffffff'
 	assert (&byte(1)).str() == '1'
-	assert byteptr(-1).str() == 'ffffffffffffffff'
-	assert byteptr(1).str() == '1'
+	assert byteptr(-1).str() == '0xffffffffffffffff'
+	assert byteptr(1).str() == '0x1'
+	assert charptr(-1).str() == '0xffffffffffffffff'
+	assert charptr(1).str() == '0x1'
 }
 
 fn test_and_precendence() {