Fix CIMTYPE CHAR16 support

The `CHAR16` fields are saved as `u16` numbers. Add support for
conversion of `u16` into a `String` if the CIMTYPE is `CIM_CHAR16`.

src/variant.rs

@@ -63,6 +63,8 @@ macro_rules! cast_num {
             Ok(Variant::R4($var as f32))
         } else if $cim_type == wbemcli::CIM_REAL64 {
             Ok(Variant::R8($var as f64))
+        } else if $cim_type == wbemcli::CIM_CHAR16 {
+            Ok(Variant::String(String::from_utf16(&[$var as u16])?))
         } else {
             Err(WMIError::ConvertVariantError(format!(
                 "Value {:?} cannot be turned into a CIMTYPE {}",
@@ -438,6 +440,14 @@ mod tests {
         assert_eq!(converted, Variant::R8(1.0));
     }
 
+    #[test]
+    fn it_convert_into_cim_char16() {
+        let cim_type = wbemcli::CIM_CHAR16;
+        let variant = Variant::UI2(67);
+        let converted = variant.convert_into_cim_type(cim_type).unwrap();
+        assert_eq!(converted, Variant::String("C".to_string()));
+    }
+
     #[test]
     fn it_convert_into_cim_type_datetime() {
         let cim_type = wbemcli::CIM_DATETIME;